In 1976, Martin et al. (J. Pharmacol. Exp. Ther. 1976, 197, 517-32) postulated that sigma receptors account for the actions of (+/xe2x88x92)-SKF 10,047 (N-allyl-normetazocine) and related racemic benzomorphans. These compounds produce a spectrum of behaviors in the dog referred to as canine delirium and have psychotomimetic effects in humans. Great interest in the hypothesis of Martin et al. concerning sigma receptors led to intense scrutiny of (+/xe2x88x92)-SKF 10,047. Ten years of additional research revealed that (+/xe2x88x92)-SKF 10,047 binds to three types of receptors: (xe2x88x92)-SKF 10,047 binds primarily to mu and kappa opiate receptors; (+)-SKF 10,047 binds to PCP receptors and to a unique site that retains the designation sigma receptor (See Quirion et al. Trends Neurosci. 1987, 10, 444-46). Sigma receptors have also been called haloperidol-sensitive sigma receptors, etorphine-inaccessible sigma receptors, and naloxone-inaccessible sigma receptors (See Walker et al. Neurology 1988, 38, 961-65).
Sigma receptors were originally thought to be a type of opiate receptor, but two subsequent findings convincingly demonstrated that this characterization was incorrect: (a) whereas opiate receptors are enantioselective for the (xe2x88x92)-isomers of opium-derived narcotics, narcotic antagonists, and their congeners, sigma receptors are enantioselective for the (+)-isomers; and (b) naloxone is ineffective against both the in vivo and in vitro effects of sigma ligands. Therefore, it became clear that the sigma receptor is not a type of opiate receptor.
Initially, investigators asserted that sigma receptors were identical with PCP receptors, based on the displacement of [3H]PCP binding by the prototypic sigma ligand (+/xe2x88x92)-SKF 10,047. For this reason, sigma receptors were sometimes called xe2x80x9csigma opiate/PCP receptorsxe2x80x9d. However, the drug selectivity pattern of [3H](+)-SKF 10,047 differs from that of [3H]PCP, showing that these substances bind to different receptors. For example, antipsychotic drugs (such as haloperidol) potently displace [3H](+)-SKF 10,047 binding, but they are weak or inactive against [3H]PCP binding. Conversely, PCP is weak antagonist of [3H]haloperidol binding.
Sigma and PCP receptors may also be differentiated by their distinct anatomical distributions, because [3H](+)-SKF 10,047 and [3H]PCP-binding sites are concentrated in different brain areas. Tam pointed out additional differences between [3H]PCP binding and [3H](+)-SKF 10,047 binding: the sensitivity of [3H]PCP binding to sodium ions; and the low affinity and small stereoselectivity shown by PCP receptors toward (+)-SKF 10,047 and (+)-ethylketocyclazocine. These findings showed that [3H](+)-SKF 10,047 binds to two distinct sites: a haloperidol-sensitive site (subsequently called the sigma receptor) and a PCP-sensitive site, subsequently called the PCP receptor.
Radioligand-binding studies revealed that many antipsychotic drugs bind to sigma receptors with high affinity. Haloperidol is among the most potent inhibitors of [3H](+)-SKF 10,047 binding, having a Ki of 4 nM (Itzhak, Y. Life Sci. 1988, 42, 745-52). Other antipsychotic drugs that possess moderate (Ki less than 1000 nM) to high potency include perphenazine, (xe2x88x92)-butaclamol, acetophenazine, trifluoperazine, molindone, pimozide, thioridazine, and chlorpromazine (Tam and Cook Proc. Natl. Acad. Sci. USA 1984, 81, 5618-21). The connection between sigma receptors and antipsychotic drugs was further strengthened by the finding that [3H]haloperidol binding is strongly reduced by the sigma ligands (+)-SKF 10,047 (+)-pentazocine, and (+)-cyclazocine. In fact, the sigma ligand (+)-pentazocine displaces [3H]haloperidol from its binding sites in guinea pig brain about 10 times more potently than the dopamine ligand spiperone.
Furthermore, sigma receptors and kappa receptors have been shown to bind the same opiates. However, kappa receptors prefer one stereoisomer, and sigma receptors prefer the other. Whereas kappa opiate receptors bind (xe2x88x92)-benzomorphans, sigma receptors bind (+)-benzomorphans. Examples are (xe2x88x92)-SKF 10,047, (xe2x88x92)-pentazocine, and (xe2x88x92)-SKF 10,047, (xe2x88x92)-pentazocine, (xe2x88x92)-cyclazocine, and (xe2x88x92)-ethylketocyclazoine, which bind to kappa opiate receptors; their (+)-enantiomers bind to sigma receptors. Another example of this distiction is found with cis and trans isomers of U50,488. Whereas the trans isomers show preference for kappa opiate receptors, the cis isomers show preference for sigma receptors. Thus, in two chemically unrelated classes of compounds, different isomers show preference for kappa or sigma receptors. These results suggest a complimentarily between the topography of the binding sites of the kappa opiate and the sigma receptor.
Haloperidol exhibits its highest affinity to the sigma site, which is distinct from the classical opiate or phencyclidine sites. See Bartoszyk, G. D. et al. CNS Drug Reviews 1996, 2, 175-94. Functional connections between sigma receptors and dopaminergic neurons in mesolimbic and cortical areas have been identified, and the involvement of sigma sites in the action of antipsychotic drugs has been shown in animal experiments. Further evidence for the significance of sigma sites in schizophrenia comes from investigations showing that benzomorphans cause symptoms that resemble schizophrenia in humans. Finally, several post-mortem studies have shown that the number of sigma binding sites in cortical and cerebellar regions is reduced in schizophrenic patients. Some attempts have been made to develop novel antipsychotic drugs with selective affinity for the sigma receptor that would not have the extrapyramidal side effects (EPS) common to the classic neuroleptics. Among these drugs, rimcazole initially has been shown to have some efficacy in humans. However, such drugs retain EPS potential, and selective sigma ligands have ultimately not shown convincing antipsychotic efficacy in clinical trials. Drugs with greater selectivity for sigma receptors, or subtypes thereof, or drugs with higher intrinsic activity hold promise, e.g., as antipsychotics.
Following the discovery that sigma receptors bind antipsychotic drugs came the expected interest in the possible clinical significance of sigma ligands. Here the question of which effects of antipsychotic drugs may be mediated by sigma receptors becomes the central focus. The high concentration of sigma receptors in the motor system immediately raised the issue of the motor side effects of antipsychotic drugs. Simultaneously, the antipsychotic activity of sigma-active drugs such as haloperidol, coupled with the sigma-activity of rimcazole (a putative antipsychotic), raised the important question of the possiblity of novel sigma-binding antipsychotic drugs.
Several attempts have been made to formulate models of the sigma receptor that can explain the SAR data for various classes of sigma ligands. Largent et al. (Mol. Pharmacol. 1987, 32, 772-84) performed conformational calculations on a total of 10 compounds, which included phenothiazines and other structures, in an attempt to determine the interatomic distances between the N-(aromatic plane) and N-(polar function). The calculated energy-minimized conformations of (xe2x88x92)-cyclazocine, cis- and trans-clopenthixol, haloperidol, and (+)-dexclamol were found to match their X-ray crystal structure conformations. This study indicated several structural requirements for sigma binding. First, the primary pharmacophore at sigma sites appears to be the 3- or 4-phenylpiperidine moiety, which is present in most compounds showing high affinity for sigma receptors. Second, affinity is greatly influenced by large hydrophobic N-alkyl substituents. Third, compounds from many different structural classes exhibit substantial affinity for sigma receptors, indicating that certain interatomic distances are not subject to rigid constraint (e.g., N to aromatic ring).
In a markedly different approach to modeling the sigma receptor, Bowen et al. (Eur. J. Pharmacol. 1989, 163, 309-18) found evidence supporting a model of distinct, allosterically-coupled binding domains for non-benzomorphan sigma ligands and sigma-related (+)-benzomorphans. Studies of the sensitivity of rat brain sigma receptors to UV irradiation revealed unusual binding interactions of the various radiolabeled sigma probes. This study suggested that benzomorphan and non-benzomorphan sigma ligands interact with different sites on the receptor macromolecule that can be distinguished by differences in their sensitivities to UV light.
A model consistent with all the results cited above, and others not explicitly discussed, is one in which benzomorphans bind to a domain on the receptor macromolecule that is resistant to the effects of UV light. Furthermore, this domain is allosterically coupled to a binding domain for non-benzomorphans. The non-benzomorphan domain is sensitive to UV irradiation, perhaps because of the presence of a LW-sensitive residue such as tryptophan.
At the present time, there does not appear to be a unifying hypothesis capable of reconciling the different topographic and structural models of the sigma receptor. However, the evidence clearly points to interaction of sigma ligands with a heterogeneous population of sites. It is also important to note that one model does not necessarily preclude another. For example, it is conceivable that there are at least two sigma receptor macromolecules, one of which consists of distinct allosterically coupled binding sites, while the other consists of a single ligand binding domain. Additionally, superimposed on these general schemes might be subtle species or tissue differences in the structure of receptor proteins that might affect the ligand-binding profiles.
Sigma receptors are concentrated in (a) brainstem areas that primarily subserve motor functions, (b) certain limbic structures, (c) some predominantly sensory areas, and (d) brain areas associated with endocrine function. See McLean and Weber Neuroscience 1988, 25, 259-69. Sigma receptors are more concentrated in motor areas than in limbic areas. The distribution in the motor system is marked by the high densities found in brainstem motor circuits. For example, the cerebellum and its closely associated circuits, the red nucleus, inferior olive and locus coeruleus, are all rich in sigma receptors. Furthermore, sigma binding is found in cranial nerve nuclei that are rich in motor neurons (facial, motor trigeminal, hypoglossal, and oculomotor, as well as in the anterior horn of the spinal cord. These data form one of several lines of evidence for a function of the sigma receptor in motor function.
Several limbic structures are labeled by sigma radioligands. These areas include the cingulate cortex, lateral and medial septum, hippocampus, hypothalamus, parts of the limbic thalamus, habenula, and anterodorsal nucleus. The presence of sigma receptors in limbic systems might suggest a rule of sigma receptors in emotion and memory. Sigma receptors are found in certain areas that are clearly related to sensory processing. Most notable among these is the heavy labeling of dorsal root ganglia by [3H](+)-3-PPP. See Gundlach et al. J. Neurosci. 1986, 6, 1757-70. The dorsal lateral geniculate and anterior pretectal areas (associated with visual information processing) are also heavily labeled by [3H]DTG.
Although the brain distribution of sigma receptors is unique, some associations with the distribution of cholinergic neurons are notable. See Sofroniew et al. In The Rat Nervous System, vol. 1, pp. 471-85, Academic Press, NY, 1985. For example, sigma receptors are rich in cranial nerve motor nuclei, spinal ventral horns, dorsal diagonal band of Broca, and septal region, all of which possess cholinergic neurons. These two receptor systems do not overlap completely, however, because the caudate, which is rich in acetylcholine, has low levels of sigma receptors.
Sigma receptors are found in many areas of the brain associated with endorcrine function. The heavy labeling over the supraoptic and paraventricular nuclei within the hypothalamus suggests that sigma receptors participate in the regulation of vasopressin (and/or dynorphin) secretion. Dense labeling was also found in the adenohypophysis, suggesting regulation of anterior pituitary hormones. Using [3H](+)-3-PPP, Jansen et al. (Brain Res. 1990, 507, 158-60) demonstrated high levels of sigma receptors in the rat pineal gland, again linking sigma receptors to endocrine function. The relation of sigma receptors to endorcrine function is further supported by the presence of sigma receptors in many peripheral endorcrine tissues.
Cell surface proteins permit intracellular transduction of extracellular signals. Cell surface proteins provide eukaryotic, as well as prokaryotic, cells a means to detect extracellular signals and transduce such signals intracellularly in a manner that ultimately results in a cellular response or a concerted tissue or organ response. Cell surface proteins, by intracellularly transmitting information regarding the extracellular environment via specific intracellular pathways induce an appropriate response to a particular stimulus. The response may be immediate and transient, slow and sustained, or some mixture thereof. By virtue of an array of varied membrane surface proteins, eukaryotic cells are exquisitely sensitive to their environment.
Extracellular signal molecules, such as ligands for the sigma receptor, vasodilators and neurotransmitters, exert their effects, at least in part, via interaction with cell surface proteins. For example, some extracellular signal molecules cause changes in transcription of target gene via changes in the levels of secondary messengers, such as cAMP. Other signals, indirectly alter gene expression by activating the expression of genes, such as immediate-early genes that encode regulatory proteins, which in turn activate expression of other genes that encode transcriptional regulatory proteins. For example, neuron gene expression is modulated by numerous extracellular signals, including neurotransmitters and membrane electrical activity. Transsynaptic signals cause rapid responses in neurons that occur over a period of time ranging from milliseconds, such as the opening of ligand-gated channels, to seconds and minutes, such as second messenger-mediated events. Genes in neural cells that are responsive to transsynaptic stimulation and membrane electrical activity, include genes, called immediate early genes, whose transcription is activated rapidly, within minutes, and transiently (See, e.g., Sheng et al. (1990) Neuron 4: 477-485), and genes whose expression requires protein synthesis and whose expression is induced or altered over the course of hours.
Cell surface-localized receptors are membrane spanning proteins that bind extracellular signalling molecules or changes in the extracellular environment and transmit the signal via signal transduction pathways to effect a cellular response. Cell surface receptors bind circulating signal polypeptides, such as growth factors and hormones, as the initiating step in the induction of numerous intracellular pathways. Receptors are classified on the basis of the particular type of pathway that is induced. Included among these classes of receptors are those that bind growth factors and have intrinsic tyrosine kinase activity, such as the heparin binding growth factor (HBGF) receptors, and those that couple to effector proteins through guanine nucleotide binding regulatory proteins, which are referred to as G protein coupled receptors and G proteins, respectively.
G proteins play a central role in several types of signaling mechanisms (See Gilman, A. G. Annu. Rev. Biochem. 1987, 56, 615-49). In some systems, the first step in the cascade of biochemical events, from the formation of a transmitter-receptor complex to membrane conductance changes, is the coupling of the receptor to a G protein. G proteins play a role in cyclic adenosine monophosphate-related systems, PPI turnover, direct coupling to some ion channels, arachidonic acid-derived systems, and protein translocation (See Casey and Gilman, J. Biol. Chem. 1988,263, 2577-80).
The G protein transmembrane signaling pathways consist of three proteins: receptors, G proteins and effectors. G proteins, which are the intermediaries in transmembrane signaling pathways, are heterodimers and consist of alpha, beta and gamma subunits. Among the members of a family of G proteins the alpha subunits differ. Functions of G proteins are regulated by the cyclic association of GTP with the alpha subunit followed by hydrolysis of GTP to GDP and dissociation of GDP.
G protein coupled receptors are a diverse class of receptors that mediate signal transduction by binding to G proteins. Signal transduction is initiated via ligand binding to the cell membrane receptor, which stimulates binding of the receptor to the G protein. The receptor G protein interaction releases GDP, which is specifically bound to the G protein, and permits the binding of GTP, which activates the G protein. Activated G protein dissociates from the receptor and activates the effector protein, which regulates the intracellular levels of specific second messengers. Examples of such effector proteins include adenyl cyclase, guanyl cyclase, phospholipase C, and others.
G protein-coupled receptors are known to be inducible. This inducibility was originally described in lower eukaryotes. For example, the cAMP receptor of the cellular slime mold, Dictyostelium, is induced during differentiation (Klein et al., Science 241: 1467-1472 (1988). During the Dictyostelium discoideum differentiation pathway, cAMP, induces high level expression of its G protein-coupled receptor. This receptor transduces the signal to induce the expression of the other genes involved in chemotaxis, which permits multicellular aggregates to align, organize and form stalks (see, Firtel, R. A., et al. Cell 58: 235-239 (1989) and Devreotes, P., Science 245: 1054-1058 (1989)).
Itzhak (See Mol. Pharmacol. 1989, 36, 512-17) reported evidence that sigma receptors interact with G proteins. As observed with other G protein-coupled receptors, guanosine triphosphate and Gpp(NY)p inhibited the binding of [3H](+)-3-PPP to rat brain membranes. Binding of [3H](+)-SKF 19m946 was also inhibited but was less affected than [3H](+)-3-PPP binding. Guanosine monophosphate and adenosine triphosphate had no effect on [3H](+)-3-PPP binding, demonstrating specificity for G protein-active guanine nucleotides. Other agents known to affect receptor-G protein coupling also inhibited [3H](+)-3-PPP binding. Treatment of rat brain membranes with either N-ethylmaleimide (a nonselective agent) or pertussis toxin (which selectively alters G proteins) significantly decreased [3H](+)-3-PPP binding. These reagents also eliminated the effect of Gpp(NH)p on [3H](+)-3-PPP binding. These results are similar to those obtained with other G protein-coupled receptors where these reagents are believed to cause uncoupling of the receptor from the G-protein unit.
Taken together, these results strongly suggest that the sigma receptor labeled by [3H](+)-3-PPP can exist in a high and low affinity state, with the high affinity state coupled to a G protein. This suggestion has important implications for the function of sigma sites, because it suggests that sigma receptors are involved in signal transduction.
One aspect of the present invention relates to spirocyclic compounds. A second aspect of the present invention relates to the use of the spirocyclic compounds as ligands for various cellular receptors, including sigma receptors and G-protein-coupled receptors. Additional aspects of the present invention relate to the synthesis of combinatorial libraries of the spirocyclic compounds, and the screening of the libraries for biological activity, e.g., in assays based on sigma receptors or G-protein-coupled receptors.
The present invention provides novel spirocyclic compounds, and combinatorial libraries thereof. Furthermore, the present invention provides spirocyclic compounds that are ligands for sigma receptors, and methods of use thereof in the treatment of conditions and diseases, wherein modulation of the activity of sigma receptors is likely to be beneficial to a subject. The present invention also relates to pharmaceutical compositions of the spirocycles.
The sigma ligands of the present invention represent new therapeutic entities in many conditions and diseases, including, but not limited to, inflammatory pain, neuropathic pain, multiple sclerosis, anxiety, depression, psychosis, stroke, motor neuron diseases, diseases associated with intraocular pressure, and glaucoma.
The ligands for sigma receptors of the present invention, in accord with eliprodil, are expected to enhance myelination in vitro. Therefore, the ligands may prove to be of therapeutic interest in demyelinating diseases like MS.
Additionally, compounds of the present invention can be tested in sigma receptor assays. Ligands for the sigma receptor can be useful as antipsychotic agents, as described in Abou-Gharbia et al., Annual Reports in Medicinal Chemistry, 28:1-10 (1993). The compounds of the invention show an especially advantageous affinity in vitro for sigma receptors, which is indicative of their usefulness in the prevention or treatment of neurological disorders and/or psychotic states.
The sigma receptor ligands of the present invention will be useful in the treatment of psychosis and movement disorders, such as dystonia and tardive dyskinesia, and motor disturbances associated with Huntington""s chorea or Tourette""s syndrome and in Parkinson""s disease (Walker, J. M. et al, Pharmacological Reviews, 1990, 42, 355). It has been reported that the known sigma receptor ligand rimcazole clinically shows effects in the treatment of psychosis (Snyder, S. H., Largent, B. L. J. Neuro-psychiatry 1989, 1. 7) and that a group of sigma receptor ligands show antihallucinogenic activity in animal models (International Patent Publication No WO 9103243).
Furthermore, the ligands for sigma receptors of the present invention will be useful as therapeutic agents for cerebral neural function disorders such as dementia, depression, schizophrenia and anxiety neurosis, diseases accompanying abnormal immune response and cryptorrhea, digestive ulcer, etc. (Journal of Neuropsychiatry, 1, 7-15 (1989); Eur. J. Biochem., 200, 633-642 (1991); J. Pharmacol. Exp. Ther., 255, 1354-1359 (1990)).
The ligands for sigma receptors of the present invention will be useful as therapeutic agents for diseases in which sigma receptors are concerned, for example, cerebral neural function disorders such as dementia, depression, schizophrenia and anxiety neurosis, diseases accompanying abnormal immune response and cryptorrhea, digestive ulcer, etc.
The ligands for sigma receptors of the present invention will modulate the effects produced by the intervention of the NMDA receptor and act as antiischemic agents in vivo (Rao, T. S. et al., Molecular Pharmacology, 1990, 37, 978), with the possibility of use as neuroprotectors and in the treatment of epilepsy and of convulsion (Kaiser C., Neurotransmissions VII, 1991). It has been said that ligands for sigma receptors exhibit antiamnesic effects in animal models (Early et al., Brain Research, 1991, 546, 281). Additionally, sigma ligands, e.g., the compounds of the present invention, influence the levels of acetylcholine in animal models (Matsun et al., Brain Research 1992, 575, 315) and can consequently be used in the treatment of senile dementia, for example of Alzheimer type.
Definitions
For convenience, certain terms employed in the specification, examples, and appended claims are collected here.
The term xe2x80x9ccell surface proteinsxe2x80x9d includes molecules that occur on the surface of cells, interact with the extracellular environment, and transmit or transduce information regarding the environment intracellularly.
The term xe2x80x9cextracellular signalsxe2x80x9d includes a molecule or a change in the environment that is transduced intracellularly via cell surface proteins that interact, directly or indirectly, with the signal. An extracellular signal is any compound or substance that in some manner specifically alters the activity of a cell surface protein. Examples of such signals include, but are not limited to, molecules such as acetylcholine, growth factors, hormones and other mitogenic substances, such as phorbol mistric acetate (PMA), that bind to cell surface receptors and ion channels and modulate the activity of such receptors and channels. Extracellular signals also includes as yet unidentified substances that modulate the activity of a cell surface protein and thereby affect intracellular functions and that are potential pharmacological agents that may be used to treat specific diseases by modulating the activity of specific cell surface receptors.
The term xe2x80x9cED50xe2x80x9d means the dose of a drug which produces 50% of its maximum response or effect. Alternatively, the dose which produces a pre-determined response in 50% of test subjects or preparations.
The term xe2x80x9cLD50xe2x80x9d means the dose of a drug which is lethal in 50% of test subjects.
The term xe2x80x9ctherapeutic indexxe2x80x9d refers to the therapeutic index of a drug defined as LD50/ED50.
The term xe2x80x9cstructure-activity relationship (SAR)xe2x80x9d refers to the way in which altering the molecular structure of drugs alters their interaction with a receptor, enzyme, etc.
The term xe2x80x9cagonistxe2x80x9d refers to a compound that mimics the action of natural transmitter or, when the natural transmitter is not known, causes changes at the receptor complex in the absence of other receptor ligands.
The term xe2x80x9cantagonistxe2x80x9d refers to a compound that binds to a receptor site, but does not cause any physiological changes unless another receptor ligand is present.
The term xe2x80x9ccompetitive antagonistxe2x80x9d refers to a compound that binds to a receptor site; its effects can be overcome by increased concentration of the agonist.
The term xe2x80x9cpartial agonistxe2x80x9d refers to a compound that binds to a receptor site but does not produce the maximal effect regardless of its concentration.
The term xe2x80x9cligandxe2x80x9d refers to a compound that binds at the receptor site.
The term xe2x80x9cheteroatomxe2x80x9d as used herein means an atom of any element other than carbon or hydrogen. Preferred heteroatoms are boron, nitrogen, oxygen, phosphorus, sulfur and selenium.
The term xe2x80x9celectron-withdrawing groupxe2x80x9d is recognized in the art, and denotes the tendency of a substituent to attract valence electrons from neighboring atoms, i.e., the substituent is electronegative with respect to neighboring atoms. A quantification of the level of electron-withdrawing capability is given by the Hammett sigma ("sgr") constant. This well known constant is described in many references, for instance, J. March, Advanced Organic Chemistry, McGraw Hill Book Company, New York, (1977 edition) pp. 251-259. The Hammett constant values are generally negative for electron donating groups ("sgr"[P]=xe2x88x920.66 for NH2) and positive for electron withdrawing groups ("sgr"[P]=0.78 for a nitro group), "sgr"[P] indicating para substitution. Exemplary electron-withdrawing groups include nitro, acyl, formyl, sulfonyl, trifluoromethyl, cyano, chloride, and the like. Exemplary electron-donating groups include amino, methoxy, and the like.
The term xe2x80x9calkylxe2x80x9d refers to the radical of saturated aliphatic groups, including straight-chain alkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic) groups, alkyl substituted cycloalkyl groups, and cycloalkyl substituted alkyl groups. In preferred embodiments, a straight chain or branched chain alkyl has 30 or fewer carbon atoms in its backbone (e.g., C1-C30 for straight chain, C3-C30 for branched chain), and more preferably 20 or fewer. Likewise, preferred cycloalkyls have from 3-10 carbon atoms in their ring structure, and more preferably have 5, 6 or 7 carbons in the ring structure.
Moreover, the term xe2x80x9calkylxe2x80x9d (or xe2x80x9clower alkylxe2x80x9d) as used throughout the specification, examples, and claims is intended to include both xe2x80x9cunsubstituted alkylsxe2x80x9d and xe2x80x9csubstituted alkylsxe2x80x9d, the latter of which refers to alkyl moieties having substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone. Such substituents can include, for example, a halogen, a hydroxyl, a carbonyl (such as a carboxyl, an alkoxycarbonyl, a formyl, or an acyl), a thiocarbonyl (such as a thioester, a thioacetate, or a thioformate), an alkoxyl, a phosphoryl, a phosphonate, a phosphinate, an amino, an amido, an amidine, an imine, a cyano, a nitro, an azido, a sulfhydryl, an alkylthio, a sulfate, a sulfonate, a sulfamoyl, a sulfonamido, a sulfonyl, a heterocyclyl, an aralkyl, or an aromatic or heteroaromatic moiety. It will be understood by those skilled in the art that the moieties substituted on the hydrocarbon chain can themselves be substituted, if appropriate. For instance, the substituents of a substituted alkyl may include substituted and unsubstituted forms of amino, azido, imino, amido, phosphoryl (including phosphonate and phosphinate), sulfonyl (including sulfate, sulfonamido, sulfamoyl and sulfonate), and silyl groups, as well as ethers, alkylthios, carbonyls (including ketones, aldehydes, carboxylates, and esters), xe2x80x94CF3, xe2x80x94CN and the like. Exemplary substituted alkyls are described below. Cycloalkyls can be further substituted with alkyls, alkenyls, alkoxys, alkylthios, aminoalkyls, carbonyl-substituted alkyls, xe2x80x94CF3, xe2x80x94CN, and the like.
The term xe2x80x9caralkylxe2x80x9d, as used herein, refers to an alkyl group substituted with an aryl group (e.g., an aromatic or heteroaromatic group).
The terms xe2x80x9calkenylxe2x80x9d and xe2x80x9calkynylxe2x80x9d refer to unsaturated aliphatic groups analogous in length and possible substitution to the alkyls described above, but that contain at least one double or triple bond respectively.
Unless the number of carbons is otherwise specified, xe2x80x9clower alkylxe2x80x9d as used herein means an alkyl group, as defined above, but having from one to ten carbons, more preferably from one to six carbon atoms in its backbone structure. Likewise, xe2x80x9clower alkenylxe2x80x9d and xe2x80x9clower alkynylxe2x80x9d have similar chain lengths. Preferred alkyl groups are lower alkyls. In preferred embodiments, a substituent designated herein as alkyl is a lower alkyl.
The term xe2x80x9carylxe2x80x9d as used herein includes 5-, 6- and 7-membered single-ring aromatic groups that may include from zero to four heteroatoms, for example, benzene, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazine and pyrimidine, and the like. Those aryl groups having heteroatoms in the ring structure may also be referred to as xe2x80x9caryl heterocyclesxe2x80x9d, xe2x80x9cheteroaromaticsxe2x80x9d, or xe2x80x9cheteroaryl.xe2x80x9d The aromatic ring can be substituted at one or more ring positions with such substituents as described above, for example, halogen, azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamido, ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromatic moieties, xe2x80x94CF3, xe2x80x94CN, or the like. The term xe2x80x9carylxe2x80x9d also includes polycyclic ring systems having two or more cyclic rings in which two or more carbons are common to two adjoining rings (the rings are xe2x80x9cfused ringsxe2x80x9d) wherein at least one of the rings is aromatic, e.g., the other cyclic rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls.
The term xe2x80x9cheteroalkylxe2x80x9d, as used herein, refers to an alkyl group wherein a carbon in the alkyl chain is substituted with a heteroatom, e.g., nitrogen, oxygen, or sulfur.
The terms xe2x80x9cheterocyclylxe2x80x9d or xe2x80x9cheterocyclic groupxe2x80x9d refer to 3- to 10-membered ring structures, more preferably 3- to 7-membered rings, whose ring structures include one to four heteroatoms. Heterocycles can also be polycycles. Heterocyclyl groups include, for example, thiophene, thianthrene, furan, pyran, isobenzofuran, chromene, xanthene, phenoxathiin, pyrrole, imidazole, pyrazole, isothiazole, isoxazole, pyridine, pyrazine, pyrimidine, pyridazine, indolizine, isoindole, indole, indazole, purine, quinolizine, isoquinoline, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, carbazole, carboline, phenanthridine, acridine, pyrimidine, phenanthroline, phenazine, phenarsazine, phenothiazine, furazan, phenoxazine, pyrrolidine, oxolane, thiolane, oxazole, piperidine, piperazine, morpholine, lactones, lactams such as azetidinones and pyrrolidinones, sultams, sultones, and the like. The heterocyclic ring can be substituted at one or more positions with such substituents as described above, as for example, halogen, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, ketone, aldehyde, ester, a heterocyclyl, an aromatic or heteroaromatic moiety, xe2x80x94CF3, xe2x80x94CN, or the like.
The terms xe2x80x9cpolycyclylxe2x80x9d or xe2x80x9cpolycyclic groupxe2x80x9d refer to two or more rings (e.g., cycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls) in which two or more carbons are common to two adjoining rings, e.g., the rings are xe2x80x9cfused ringsxe2x80x9d. Rings that are joined through non-adjacent atoms are termed xe2x80x9cbridgedxe2x80x9d rings. Each of the rings of the polycycle can be substituted with such substituents as described above, as for example, halogen, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, ketone, aldehyde, ester, a heterocyclyl, an aromatic or heteroaromatic moiety, xe2x80x94CF3, xe2x80x94CN, or the like.
The terms xe2x80x9cspirocyclexe2x80x9d and xe2x80x9cspirocyclicxe2x80x9d refer to compounds or moieties wherein two rings have in common only a single carbon or silicon atom. 
The term xe2x80x9ccarbocyclexe2x80x9d, as used herein, refers to an aromatic or non-aromatic ring in which each atom of the ring is carbon.
As used herein, the term xe2x80x9cnitroxe2x80x9d means xe2x80x94NO2; the term xe2x80x9chalogenxe2x80x9d designates xe2x80x94F, xe2x80x94Cl, xe2x80x94Br or xe2x80x94I; the term xe2x80x9csulfhydrylxe2x80x9d means xe2x80x94SH; the term xe2x80x9chydroxylxe2x80x9d means xe2x80x94OH; and the term xe2x80x9csulfonylxe2x80x9d means xe2x80x94SO2xe2x80x94.
The terms xe2x80x9caminexe2x80x9d and xe2x80x9caminoxe2x80x9d are art-recognized and refer to both unsubstituted and substituted amines, e.g., a moiety that can be represented by the general formula: 
wherein R9, R10 and Rxe2x80x210 each independently represent a hydrogen, an alkyl, an alkenyl, xe2x80x94(CH2)mxe2x80x94R8, or R9 and R10 taken together with the N atom to which they are attached complete a heterocycle having from 4 to 8 atoms in the ring structure; R8 represents an aryl, a cycloalkyl, a cycloalkenyl, a heterocycle or a polycycle; and m is zero or an integer in the range of 1 to 8. In preferred embodiments, only one of R9 or R10 can be a carbonyl, e.g., R9, R10 and the nitrogen together do not form an imide. In even more preferred embodiments, R9 and R10 (and optionally Rxe2x80x210) each independently represent a hydrogen, an alkyl, an alkenyl, or xe2x80x94(CH2)mxe2x80x94R8. Thus, the term xe2x80x9calkylaminexe2x80x9d as used herein means an amine group, as defined above, having a substituted or unsubstituted alkyl attached thereto, i.e., at least one of R9 and R10 is an alkyl group.
The term xe2x80x9cacylaminoxe2x80x9d is art-recognized and refers to a moiety that can be represented by the general formula: 
wherein R9 is as defined above, and Rxe2x80x211 represents a hydrogen, an alkyl, an alkenyl or xe2x80x94(CH2)mxe2x80x94R8, where m and R8 are as defined above.
The term xe2x80x9camidoxe2x80x9d is art recognized as an amino-substituted carbonyl and includes a moiety that can be represented by the general formula: 
wherein R9, R10 are as defined above. Preferred embodiments of the amide will not include imides which may be unstable.
The term xe2x80x9calkylthioxe2x80x9d refers to an alkyl group, as defined above, having a sulfur radical attached thereto. In preferred embodiments, the xe2x80x9calkylthioxe2x80x9d moiety is represented by one of xe2x80x94S-alkyl, xe2x80x94S-alkenyl, xe2x80x94S-alkynyl, and xe2x80x94Sxe2x80x94(CH2)mxe2x80x94R8, wherein m and R8 are defined above. Representative alkylthio groups include methylthio, ethyl thio, and the like.
The term xe2x80x9ccarbonylxe2x80x9d is art recognized and includes such moieties as can be represented by the general formula: 
wherein X is a bond or represents an oxygen or a sulfur, and R11 represents a hydrogen, an alkyl, an alkenyl, xe2x80x94(CH2)mxe2x80x94R8 or a pharmaceutically acceptable salt, Rxe2x80x211 represents a hydrogen, an alkyl, an alkenyl or xe2x80x94(CH2)mxe2x80x94R8, where m and R8 are as defined above. Where X is an oxygen and R11 or Rxe2x80x211 is not hydrogen, the formula represents an xe2x80x9cesterxe2x80x9d. Where X is an oxygen, and R11 is as defined above, the moiety is referred to herein as a carboxyl group, and particularly when R11 is a hydrogen, the formula represents a xe2x80x9ccarboxylic acidxe2x80x9d. Where X is an oxygen, and Rxe2x80x211 is hydrogen, the formula represents a xe2x80x9cformatexe2x80x9d. In general, where the oxygen atom of the above formula is replaced by sulfur, the formula represents a xe2x80x9cthiolcarbonylxe2x80x9d group. Where X is a sulfur and R11 or Rxe2x80x211 is not hydrogen, the formula represents a xe2x80x9cthiolester.xe2x80x9d Where X is a sulfur and R11 is hydrogen, the formula represents a xe2x80x9cthiolcarboxylic acid.xe2x80x9d Where X is a sulfur and R11xe2x80x2 is hydrogen, the formula represents a xe2x80x9cthiolformate.xe2x80x9d On the other hand, where X is a bond, and R11 is not hydrogen, the above formula represents a xe2x80x9cketonexe2x80x9d group. Where X is a bond, and R11 is hydrogen, the above formula represents an xe2x80x9caldehydexe2x80x9d group.
The terms xe2x80x9calkoxylxe2x80x9d or xe2x80x9calkoxyxe2x80x9d as used herein refers to an alkyl group, as defined above, having an oxygen radical attached thereto. Representative alkoxyl groups include methoxy, ethoxy, propyloxy, tert-butoxy and the like. An xe2x80x9cetherxe2x80x9d is two hydrocarbons covalently linked by an oxygen. Accordingly, the substituent of an alkyl that renders that alkyl an ether is or resembles an alkoxyl, such as can be represented by one of xe2x80x94O-alkyl, xe2x80x94O-alkenyl, xe2x80x94O-alkynyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94R8, where m and R8 are described above.
The term xe2x80x9csulfonatexe2x80x9d is art recognized and includes a moiety that can be represented by the general formula: 
in which R41 is an electron pair, hydrogen, alkyl, cycloalkyl, or aryl.
The terms triflyl, tosyl, mesyl, and nonaflyl are art-recognized and refer to trifluoromethanesulfonyl, p-toluenesulfonyl, methanesulfonyl, and nonafluorobutanesulfonyl groups, respectively. The terms triflate, tosylate, mesylate, and nonaflate are art-recognized and refer to trifluoromethanesulfonate ester, p-toluenesulfonate ester, methanesulfonate ester, and nonafluorobutanesulfonate ester functional groups and molecules that contain said groups, respectively.
The abbreviations Me, Et, Ph, Tf, Nf, Ts, Ms represent methyl, ethyl, phenyl, trifluoromethanesulfonyl, nonafluorobutanesulfonyl, p-toluenesulfonyl and methanesulfonyl, respectively. A more comprehensive list of the abbreviations utilized by organic chemists of ordinary skill in the art appears in the first issue of each volume of the Journal of Organic Chemistry; this list is typically presented in a table entitled Standard List of Abbreviations. The abbreviations contained in said list, and all abbreviations utilized by organic chemists of ordinary skill in the art are hereby incorporated by reference.
The term xe2x80x9csulfatexe2x80x9d is art recognized and includes a moiety that can be represented by the general formula: 
in which R41 is as defined above.
The term xe2x80x9csulfonamidoxe2x80x9d is art recognized and includes a moiety that can be represented by the general formula: 
in which R9 and Rxe2x80x211 are as defined above.
The term xe2x80x9csulfamoylxe2x80x9d is art-recognized and includes a moiety that can be represented by the general formula: 
in which R9 and R10 are as defined above.
The term xe2x80x9csulfonylxe2x80x9d, as used herein, refers to a moiety that can be represented by the general formula: 
in which R44 is selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl.
The term xe2x80x9csulfoxidoxe2x80x9d as used herein, refers to a moiety that can be represented by the general formula: 
in which R44 is selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aralkyl, or aryl.
A xe2x80x9cphosphorylxe2x80x9d can in general be represented by the formula: 
wherein Q1 represented S or O, and R46 represents hydrogen, a lower alkyl or an aryl. When used to substitute, e.g., an alkyl, the phosphoryl group of the phosphorylalkyl can be represented by the general formula: 
wherein Q1 represented S or O, and each R46 independently represents hydrogen, a lower alkyl or an aryl, Q2 represents O, S or N. When Q1 is an S, the phosphoryl moiety is a xe2x80x9cphosphorothioatexe2x80x9d.
A xe2x80x9cselenoalkylxe2x80x9d refers to an alkyl group having a substituted seleno group attached thereto. Exemplary xe2x80x9cselenoethersxe2x80x9d which may be substituted on the alkyl are selected from one of xe2x80x94Se-alkyl, xe2x80x94Se-alkenyl, xe2x80x94Se-alkynyl, and xe2x80x94Sexe2x80x94(CH2)mxe2x80x94R7, m and R7 being defined above.
Analogous substitutions can be made to alkenyl and alkynyl groups to produce, for example, aminoalkenyls, aminoalkynyls, amidoalkenyls, amidoalkynyls, iminoalkenyls, iminoalkynyls, thioalkenyls, thioalkynyls, carbonyl-substituted alkenyls or alkynyls.
As used herein, the definition of each expression, e.g. alkyl, m, n, etc., when it occurs more than once in any structure, is intended to be independent of its definition elsewhere in the same structure.
It will be understood that xe2x80x9csubstitutionxe2x80x9d or xe2x80x9csubstituted withxe2x80x9d includes the implicit proviso that such substitution is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution results in a stable compound, e.g., which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc.
As used herein, the term xe2x80x9csubstitutedxe2x80x9d is contemplated to include all permissible substituents of organic compounds. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic substituents of organic compounds. Illustrative substituents include, for example, those described herein above. The permissible substituents can be one or more and the same or different for appropriate organic compounds. For purposes of this invention, the heteroatoms such as nitrogen may have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the valences of the heteroatoms. This invention is not intended to be limited in any manner by the permissible substituents of organic compounds.
The phrase xe2x80x9cprotecting groupxe2x80x9d as used herein means temporary substituents which protect a potentially reactive functional group from undesired chemical transformations. Examples of such protecting groups include esters of carboxylic acids, silyl ethers of alcohols, and acetals and ketals of aldehydes and ketones, respectively. The field of protecting group chemistry has been reviewed (Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, b 2nd ed.; Wiley: N.Y., 1991).
Certain compounds of the present invention may exist in particular geometric or stereoisomeric forms. The present invention contemplates all such compounds, including cis- and trans-isomers, R- and S-enantiomers, diastereomers, (D)-isomers, (L)-isomers, the racemic mixtures thereof, and other mixtures thereof, as falling within the scope of the invention. Additional asymmetric carbon atoms may be present in a substituent such as an alkyl group. All such isomers, as well as mixtures thereof, are intended to be included in this invention.
If, for instance, a particular enantiomer of a compound of the present invention is desired, it may be prepared by asymmetric synthesis, or by derivation with a chiral auxiliary, where the resulting diastereomeric mixture is separated and the auxiliary group cleaved to provide the pure desired enantiomers. Alternatively, where the molecule contains a basic functional group, such as amino, or an acidic functional group, such as carboxyl, diastereomeric salts are formed with an appropriate optically-active acid or base, followed by resolution of the diastereomers thus formed by fractional crystallization or chromatographic means well known in the art, and subsequent recovery of the pure enantiomers.
Contemplated equivalents of the compounds described above include compounds which otherwise correspond thereto, and which have the same general properties thereof (e.g., functioning as analgesics), wherein one or more simple variations of substituents are made which do not adversely affect the efficacy of the compound in binding to sigma receptors. In general, the compounds of the present invention may be prepared by the methods illustrated in the general reaction schemes as, for example, described below, or by modifications thereof, using readily available starting materials, reagents and conventional synthesis procedures. In these reactions, it is also possible to make use of variants which are in themselves known, but are not mentioned here.
For purposes of this invention, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 67th Ed., 1986-87, inside cover. Also for purposes of this invention, the term xe2x80x9chydrocarbonxe2x80x9d is contemplated to include all permissible compounds having at least one hydrogen and one carbon atom. In a broad aspect, the permissible hydrocarbons include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic organic compounds which can be substituted or unsubstituted.
In certain embodiments, the compounds of the present invention are represented by structure 1: 
wherein
R represents independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R1 is absent, or present between 1 and 4 times;
R1 represents independently for each occurrence halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, silyloxy, amino, nitro, sulfhydryl, alkylthio, imine, amide, phosphoryl, phosphonate, phosphine, carbonyl, carboxyl, carboxamide, anhydride, silyl, thioalkyl, alkylsulfonyl, arylsulfonyl, selenoalkyl, ketone, aldehyde, ester, heteroalkyl, nitrile, guanidine, amidine, acetal, ketal, amine oxide, aryl, heteroaryl, aralkyl, heteroaralkyl, azide, aziridine, carbamate, epoxide, hydroxamic acid, imide, oxime, sulfonamide, thioamide, thiocarbamate, urea, thiourea, or xe2x80x94(CH2)mxe2x80x94R80;
R2 and R3 represent independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, OR, N(R)2, CO2R, C(O)N(R)2, OC(O)R, or N(R)C(O)R; or two geminal instances of R2 and R3 taken together may represent O or C(R)2;
R6 represents hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R7 represents hydrogen, alkyl, alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R80 represents an aryl, cycloalkyl, cycloalkenyl, heterocyclyl, or polycyclyl group;
m is an integer in the range 0 to 8 inclusive; and
n is 1, 2, or 3;
provided that when n is 3 and a pair of geminal instances of R2 and R3 taken together represent O, R7 is not acetyl;
further provided that when n is 2, R2 and R3 are not both methyl; or when n is 2, R6 and R7 are not both acetyl.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein at least one pair of geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and at least one pair of geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; at least one pair of geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and at least one pair of geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 1 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; at least one pair of geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain assays based on mammalian G-protein-coupled receptors or sigma receptors, certain compounds according to general structure 1 have IC50 values less than 10 xcexcM, more preferably less than 1 xcexcM, and most preferably less than 0.1 xcexcM.
In certain embodiments, the compounds of the present invention are represented by structure 2: 
wherein
R represents independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R1 is absent, or present between 1 and 4 times;
R1 represents independently for each occurrence halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, silyloxy, amino, nitro, sulfhydryl, alkylthio, imine, amide, phosphoryl, phosphonate, phosphine, carbonyl, carboxyl, carboxamide, anhydride, silyl, thioalkyl, alkylsulfonyl, arylsulfonyl, selenoalkyl, ketone, aldehyde, ester, heteroalkyl, nitrile, guanidine, amidine, acetal, ketal, amine oxide, aryl, heteroaryl, aralkyl, heteroaralkyl, azide, aziridine, carbamate, epoxide, hydroxamic acid, imide, oxime, sulfonamide, thioamide, thiocarbamate, urea, thiourea, or xe2x80x94(CH2)mxe2x80x94R80;
R2 and R3 represent independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, OR, N(R)2, CO2R, C(O)N(R)2, OC(O)R, or N(R)C(O)R; or the geminal instances of R2 and R3 taken together may represent O or C(R)2;
R6 represents hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R7 represents hydrogen, alkyl, alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R80 represents an aryl, cycloalkyl, cycloalkenyl, heterocyclyl, or polycyclyl group; and
m is an integer in the range 0 to 8 inclusive;
provided that when the geminal instances of R2 and R3 taken together represent O, R7 is not acetyl.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 2 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain assays based on mammalian G-protein-coupled receptors or sigma receptors, certain compounds according to general structure 2 have IC50 values less than 10 xcexcM, more preferably less than 1 xcexcM, and most preferably less than 0.1 xcexcM.
In certain embodiments, the compounds of the present invention are represented by structure 3: 
wherein
R represents independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R1 is absent, or present between 1 and 4 times;
R1 represents independently for each occurrence halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, silyloxy, amino, nitro, sulfhydryl, alkylthio, imine, amide, phosphoryl, phosphonate, phosphine, carbonyl, carboxyl, carboxamide, anhydride, silyl, thioalkyl, alkylsulfonyl, arylsulfonyl, selenoalkyl, ketone, aldehyde, ester, heteroalkyl, nitrile, guanidine, amidine, acetal, ketal, amine oxide, aryl, heteroaryl, aralkyl, heteroaralkyl, azide, aziridine, carbamate, epoxide, hydroxamic acid, imide, oxime, sulfonamide, thioamide, thiocarbamate, urea, thiourea, or xe2x80x94(CH2)mxe2x80x94R80;
R2 and R3 represent independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, OR, N(R)2, CO2R, C(O)N(R)2, OC(O)R, or N(R)C(O)R; or the geminal instances of R2 and R3 taken together may represent O or C(R)2;
R4 represents independently for each occurrence H or alkyl;
R6 represents hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R7 represents hydrogen, alkyl, alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R80 represents an aryl, cycloalkyl, cycloalkenyl, heterocyclyl, or polycyclyl group;
m is an integer in the range 0 to 8 inclusive; and
n is 0 or 1;
provided that when the geminal instances of R2 and R3 taken together represent O, R7 is not acetyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R4 represents independently for each occurrence H.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 3 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain assays based on mammalian G-protein-coupled receptors or sigma receptors, certain compounds according to general structure 3 have IC50 values less than 10 xcexcM, more preferably less than 1 xcexcM, and most preferably less than 0.1 xcexcM.
In certain embodiments, the compounds of the present invention are represented by structure 4: 
wherein
R represents independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R1 is absent, or present between 1 and 4 times;
R1 represents independently for each occurrence halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, silyloxy, amino, nitro, sulfhydryl, alkylthio, imine, amide, phosphoryl, phosphonate, phosphine, carbonyl, carboxyl, carboxamide, anhydride, silyl, thioalkyl, alkylsulfonyl, arylsulfonyl, selenoalkyl, ketone, aldehyde, ester, heteroalkyl, nitrile, guanidine, amidine, acetal, ketal, amine oxide, aryl, heteroaryl, aralkyl, heteroaralkyl, azide, aziridine, carbamate, epoxide, hydroxamic acid, imide, oxime, sulfonamide, thioamide, thiocarbamate, urea, thiourea, or xe2x80x94(CH2)mxe2x80x94R80;
R2 and R3 represent independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, OR, N(R)2, CO2R, C(O)N(R)2, OC(O)R, or N(R)C(O)R; or the geminal instances of R2 and R3 taken together may represent O or C(R)2;
R6 represents hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R7 represents hydrogen, alkyl, alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R80 represents an aryl, cycloalkyl, cycloalkenyl, heterocyclyl, or polycyclyl group; and
m is an integer in the range 0 to 8 inclusive;
provided that R2 and R3 are not both methyl; or R6 and R7 are not both acetyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 4 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain assays based on mammalian G-protein-coupled receptors or sigma receptors, certain compounds according to general structure 4 have IC50 values less than 10 xcexcM, more preferably less than 1 xcexcM, and most preferably less than 0.1 xcexcM.
In certain embodiments, the compounds of the present invention are represented by structure 5: 
wherein
R represents independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl;
R1 is absent, or present between 1 and 4 times;
R1 represents independently for each occurrence halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, silyloxy, amino, nitro, sulfhydryl, alkylthio, imine, amide, phosphoryl, phosphonate, phosphine, carbonyl, carboxyl, carboxamide, anhydride, silyl, thioalkyl, alkylsulfonyl, arylsulfonyl, selenoalkyl, ketone, aldehyde, ester, heteroalkyl, nitrile, guanidine, amidine, acetal, ketal, amine oxide, aryl, heteroaryl, aralkyl, heteroaralkyl, azide, aziridine, carbamate, epoxide, hydroxamic acid, imide, oxime, sulfonamide, thioamide, thiocarbamate, urea, thiourea, or xe2x80x94(CH2)mxe2x80x94R80;
R2 and R3 represent independently for each occurrence hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, OR, N(R)2, CO2R, C(O)N(R)2, OC(O)R, or N(R)C(O)R; or the geminal instances of R2 and R3 taken together may represent O or C(R)2;
R6 represents hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R7 represents hydrogen, alkyl, alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, acyl, C(O)OR, C(O)N(R)2, or SO2R;
R80 represents an aryl, cycloalkyl, cycloalkenyl, heterocyclyl, or polycyclyl group; and m is an integer in the range 0 to 8 inclusive.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, N(R)2, halogen, CO2R, CON(R)2, OCF3, CN, or CF3; the geminal instances of R2 and R3 taken together represent O; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and R2 and R3 represent independently for each occurrence H, OR, or N(R)2.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; and the geminal instances of R2 and R3 taken together represent O.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; and R6 represents H, alkyl or acyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; R2 and R3 represent independently for each occurrence H, OR, or N(R)2; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain embodiments, the compounds of the present invention are represented by structure 5 and the attendant definitions, wherein R1 represents independently for each occurrence OR, halogen, or CF3; the geminal instances of R2 and R3 taken together represent O; R6 represents H, alkyl or acyl; and R7 represents H, alkyl or aralkyl.
In certain assays based on mammalian G-protein-coupled receptors or sigma receptors, certain compounds according to general structure 5 have IC50 values less than 10 xcexcM, more preferably less than 1 xcexcM, and most preferably less than 0.1 xcexcM.
In certain embodiments, the present invention relates to ligands for G-protein-coupled or sigma receptors, wherein the ligands are represented by any of generalized structures outlined above, and any of the sets of definitions associated with one of those structures. Preferably, the ligands of the present invention are antagonists or agonists of G-protein-coupled or sigma receptors. In any event, the ligands of the present invention preferably exert their effect on the receptors at a concentration less than about 10 micromolar, more preferably at a concentration less than about 1 micromolar, and most preferably at a concentration less than 100 nanomolar. In certain embodiments, the ligands of the present invention bind selectively to a single family of G-protein-coupled or sigma receptors. In other embodiments, the ligands of the present invention bind selectively to a subtype of receptor within a family of G-protein-coupled or sigma receptors.
In certain embodiments, the selectivity of a ligand for a specific family or subtype of receptor renders that ligand an effective therapeutic agent for an acute or chronic ailment, disease or malady. In certain embodiments, the selectivity of a ligand for a specific family or subtype of receptor consists of a binding affinity for that family or subtype of receptor at least a factor of ten greater than its binding affinity for other families or subtypes of G-protein-coupled or sigma receptors. In preferred embodiments, the selectivity of a ligand for a specific family or subtype of receptor consists of a binding affinity for that family or subtype of receptor at least a factor of one hundred greater than its binding affinity for other families or subtypes of G-protein-coupled or sigma receptors. In certain embodiments, the selectivity of a ligand for a specific family or subtype of receptor consists of a binding affinity for that family or subtype of receptor at least a factor of one thousand greater than its binding affinity for other families or subtypes of G-protein-coupled or sigma receptors.
The present invention contemplates pharmaceutical formulations (see below) of the ligands of the present invention. In certain embodiments, the pharmaceutical formulations will comprise ligands of the present invention that effect only a specific family or subtype of G-protein-coupled or sigma receptor, and thereby have a therapeutic effect on an acute or chronic ailment, disease or malady that is at least in part due to biochemical or physiological processes associated with the receptor(s). In preferred embodiments, the pharmaceutical formulations will comprise ligands of the present invention that effect only a subtype of receptor, and thereby have a therapeutic effect on an acute or chronic ailment, disease or malady that is at least in part due to biochemical or physiological processes associated with the specific subtype of receptor. The Background of the Invention (see above) teaches examples of acute or chronic ailments, diseases or maladies that are caused or exacerbated by biochemical or physiological processes associated with specific G-protein-coupled or sigma receptors. One of ordinary skill in the art will be able to accumulate, by reference to the scientific literature, a more comprehensive list of acute or chronic ailments, diseases or maladies that are caused or exacerbated by biochemical or physiological processes associated with specific G-protein-coupled or sigma receptors. The present invention contemplates pharmaceutical formulations of ligands of the present invention that will be of medicinal value against the aforementioned acute or chronic ailments, diseases or maladies.
Biochemical Activity at Cellular Receptors, and Assays to Detect It
Assaying processes are well known in the art in which a reagent is added to a sample, and measurements of the sample and reagent are made to identify sample attributes stimulated by the reagent. For example, one such assay process concerns determining in a chromogenic assay the amount of an enzyme present in a biological sample or solution. Such assays are based on the development of a colored product in the reaction solution. The reaction develops as the enzyme catalyzes the conversion of a colorless chromogenic substrate to a colored product.
Assays useful in the present invention concern determining the activity of receptors the activation of which initiates subsequent intracellular events in which intracellular stores of calcium ions are released for use as a second messenger. Activation of some G-protein-coupled receptors stimulates the formation of inositol triphosphate (IP3, a G-protein-coupled receptor second messenger) through phospholipase C-mediated hydrolysis of phosphatidylinositol, Berridge and Irvine (1984). Nature 312:315-21. IP3 in turn stimulates the release of intracellular calcium ion stores.
A change in cytoplasmic calcium ion levels caused by release of calcium ions from intracellular stores is used to determine G-protein-coupled receptor function. This is another type of indirect assay. Among G-protein-coupled receptors are muscarinic acetylcholine receptors (mAChR), adrenergic receptors, serotonin receptors, dopamine receptors, angiotensin receptors, adenosine receptors, bradykinin receptors, metabotropic excitatory amino acid receptors and the like. Cells expressing such G-protein-coupled receptors may exhibit increased cytoplasmic calcium levels as a result of contribution from both intracellular stores and via activation of ion channels, in which case it may be desirable although not necessary to conduct such assays in calcium-free buffer, optionally supplemented with a chelating agent such as EGTA, to distinguish fluorescence response resulting from calcium release from internal stores. Another type of indirect assay involves determining the activity of receptors which, when activated, result in a change in the level of intracellular cyclic nucleotides, e.g., cAMP, cGMP. For example, activation of some dopamine, serotonin, metabotropic glutamate receptors and muscarinic acetylcholine receptors results in a decrease in the cAMP or cGMP levels of the cytoplasm.
Furthermore, there are cyclic nucleotide-gated ion channels, e.g., rod photoreceptor cell channels and olfactory neuron channels [see, Altenhofen, W. et al. (1991) Proc. Natl. Acad. Sci U.S.A. 88:9868-9872 and Dhallan et al. (1990) Nature 347:184-187] that are permeable to cations upon activation by binding of cAMP or cGMP. A change in cytoplasmic ion levels caused by a change in the amount of cyclic nucleotide activation of photo-receptor or olfactory neuron channels is used to determine function of receptors that cause a change in cAMP or cGMP levels when activated. In cases where activation of the receptor results in a decrease in cyclic nucleotide levels, it may be preferable to expose the cells to agents that increase intracellular cyclic nucleotide levels, e.g., forskolin, prior to adding a receptor-activating compound to the cells in the assay. Cell for this type of assay can be made by co-transfection of a host cell with DNA encoding a cyclic nucleotide-gated ion channel and a DNA encoding a receptor (e.g., certain metabotropic glutamate receptors, muscarinic acetylcholine receptors, dopamine receptors, serotonin receptors and the like, which, when activated, causes a change in cyclic nucleotide levels in the cytoplasm.
Any cell expressing a receptor protein which is capable, upon activation, of directly increasing the intracellular concentration of calcium, such as by opening gated calcium channels, or indirectly affecting the concentration of intracellular calcium as by causing initiation of a reaction which utilizes Ca less than 2+ greater than  as a second messenger (e.g., G-protein-coupled receptors), may form the basis of an assay. Cells endogenously expressing such receptors or ion channels and cells which may be transfected with a suitable vector encoding one or more such cell surface proteins are known to those of skill in the art or may be identified by those of skill in the art. Although essentially any cell which expresses endogenous ion channel and/or receptor activity may be used, it is preferred to use cells transformed or transfected with heterologous DNAs encoding such ion channels and/or receptors so as to express predominantly a single type of ion channel or receptor. Many cells that may be genetically engineered to express a heterologous cell surface protein are known. Such cells include, but are not limited to, baby hamster kidney (BHK) cells (ATCC No. CCL10), mouse L cells (ATCC No. CCLI.3), DG44 cells [see, Chasin (1986) Cell. Molec. Genet. 12:555] human embryonic kidney (HEK) cells (ATCC No. CRL1573), Chinese hamster ovary (CHO) cells (ATCC Nos. CRL9618, CCL61, CRL9096), PC12 cells (ATCC No. CRL1721) and COS-7 cells (ATCC No. CRL1651). Preferred cells for heterologous cell surface protein expression are those that can be readily and efficiently transfected. Preferred cells include HEK 293 cells, such as those described in U.S. Pat. No. 5,024,939.
Any compound which is known to activate ion channels or receptors of interest may be used to initiate an assay. Choosing an appropriate ion channel- or receptor-activating reagent depending on the ion channel or receptor of interest is within the skill of the art. Direct depolarization of the cell membrane to determine calcium channel activity may be accomplished by adding a potassium salt solution having a concentration of potassium ions such that the final concentration of potassium ions in the cell-containing well is in the range of about 50-150 mM (e.g., 50 mM KCl). With respect to ligand-gated receptors and ligand-gated ion channels, ligands are known which have affinity for and activate such receptors. For example, nicotinic acetyloholine receptors are known to be activated by nicotine or acetylcholine; similarly, muscarinic acetylcholine receptors may be activated by addition of muscarine or carbamylcholine.
Agonist assays may be carried out on cells known to possess ion channels and/or receptors to determine what effect, if any, a compound has on activation or potentiation of ion channels or receptors of interest. Agonist assays also may be carried out using a reagent known to possess ion channel- or receptor-activating capacity to determine whether a cell expresses the respective functional ion channel or receptor of interest.
Contacting a functional receptor or ion channel with agonist typically activates a transient reaction; and prolonged exposure to an agonist may desensitize the receptor or ion channel to subsequent activation. Thus, in general, assays for determining ion channel or receptor function should be initiated by addition of agonist (i.e., in a reagent solution used to initiate the reaction). The potency of a compound having agonist activity is determined by the detected change in some observable in the cells (typically an increase, although activation of certain receptors causes a decrease) as compared to the level of the observable in either the same cell, or substantially identical cell, which is treated substantially identically except that reagent lacking the agonist (i.e., control) is added to the well. Where an agonist assay is performed to test whether or not a cell expresses the functional receptor or ion channel of interest, known agonist is added to test-cell-containing wells and to wells containing control cells (substantially identical cell that lacks the specific receptors or ion channels) and the levels of observable are compared. Depending on the assay, cells lacking the ion channel and/or receptor of interest should exhibit substantially no increase in observable in response to the known agonist. A substantially identical cell may be derived from the same cells from which recombinant cells are prepared but which have not been modified by introduction of heterologous DNA. Alternatively, it may be a cell in which the specific receptors or ion channels are removed. Any statistically or otherwise significant difference in the level of observable indicates that the test compound has in some manner altered the activity of the specific receptor or ion channel or that the test cell possesses the specific functional receptor or ion channel.
In an example of drug screening assays for identifying compounds which have the ability to modulate ion channels or receptors of interest, individual wells (or duplicate wells, etc.) contain a distinct cell type, or distinct recombinant cell line expressing a homogeneous population of a receptor or ion channel of interest, so that the compound having unidentified activity may be screened to determine whether it possesses modulatory activity with respect to one or more of a variety of functional ion channels or receptors. It is also contemplated that each of the individual wells may contain the same cell type so that multiple compounds (obtained from different reagent sources in the apparatus or contained within different wells) can be screened and compared for modulating activity with respect to one particular receptor or ion channel type.
Antagonist assays, including drug screening assays, may be carried out by incubating cells having functional ion channels and/or receptors in the presence and absence of one or more compounds, added to the solution bathing the cells in the respective wells of the microtiter plate for an amount of time sufficient (to the extent that the compound has affinity for the ion channel and/or receptor of interest) for the compound(s) to bind to the receptors and/or ion channels, then activating the ion channels or receptors by addition of known agonist, and measuring the level of observable in the cells as compared to the level of observable in either the same cell, or substantially identical cell, in the absence of the putative antagonist.
The assays are thus useful for rapidly screening compounds to identify those that modulate any receptor or ion channel in a cell. In particular, assays can be used to test functional ligand-receptor or ligand-ion channel interactions for cell receptors including ligand-gated ion channels, voltage-gated ion channels, G-protein-coupled receptors and growth factor receptors.
Those of ordinary skill in the art will recognize that assays may encompass measuring a detectable change of a solution as a consequence of a cellular event which allows a compound, capable of differential characteristics, to change its characteristics in response to the cellular event. By selecting a particular compound which is capable of differential characteristics upon the occurrence of a cellular event, various assays may be performed. For example, assays for determining the capacity of a compound to induce cell injury or cell death may be carried out by loading the cells with a pH-sensitive fluorescent indicator such as BCECF (Molecular Probes, Inc., Eugene, Oreg. 97402, Catalog #B1150) and measuring cell injury or cell death as a function of changing fluorescence over time.
Sigma receptor binding assays using guinea pig brain membrane homogenates and the radioligand [ less than 3 greater than  H]DTG may be conducted as described by Weber et al., Proc. Natl. Acad. Sci. USA 83:8784-8788 (1986). Furthermore, assays for binding to sigma receptors which rely on a guinea pig brain (less the cerebellum) homogenate may be used, in a modification of the process of L. Radesca et al., J. Med. Chem., 34, 3058-3065 (1991). In this system, [3H]-(+)-3-PPP is used as radioligand and haloperidol is used for measuring the non-specific binding. The inhibition constants (Ki, nM) may be calculated by non-linear regression analysis by using the EBDA/LIGAND program (Munson and Rodbard, Analytical Biochemistry, 107, 220 (1980)).
In a further example of useful assays, the function of receptors whose activation results in a change in the cyclic nucleotide levels of the cytoplasm may be directly determined in assays of cells that express such receptors and that have been injected with a fluorescent compound that changes fluorescence upon binding cAMP. The fluorescent compound comprises cAMP-dependent-protein kinase in which the catalytic and regulatory subunits are each labelled with a different fluorescent-dye [Adams et al. (1991) Nature 349:694-697]. When cAMP binds to the regulatory subunits, the fluorescence emission spectrum changes; this change can be used as an indication of a change in cAMP concentration.
The function of certain neurotransmitter transporters which are present at the synaptic cleft at the junction between two neurons may be determined by the development of fluorescence in the cytoplasm of such neurons when conjugates of an amine acid and fluorescent indicator (wherein the fluorescent indicator of the conjugate is an acetoxymethyl ester derivative e.g., 5-(aminoacetamido)fluorescein; Molecular Probes, Catalog #A1363) are transported by the neurotransmitter transporter into the cytoplasm of the cell where the ester group is cleaved by esterase activity and the conjugate becomes fluorescent.
In practicing an assay of this type, a reporter gene construct is inserted into an eukaryotic cell to produce a recombinant cell which has present on its surface a cell surface protein of a specific type. The cell surface receptor may be endogenously expressed or it may be expressed from a heterologous gene that has been introduced into the cell. Methods for introducing heterologous DNA into eukaryotic cells are-well known in the art and any such method may be used. In addition, DNA encoding various cell surface proteins is known to those of skill in the art or it may be cloned by any method known to those of skill in the art.
The recombinant cell is contacted with a test compound and the level of reporter gene expression is measured. The contacting may be effected in any vehicle and the testing may be by any means using any protocols, such as serial dilution, for assessing specific molecular interactions known to those of skill in the art. After contacting the recombinant cell for a sufficient time to effect any interactions, the level of gene expression is measured. The amount of time to effect such interactions may be empirically determined, such as by running a time course and measuring the level of transcription as a function of time. The amount of transcription may be measured using any method known to those of skill in the art to be suitable. For example, specific mRNA expression may be detected using Northern blots or specific protein product may be identified by a characteristic stain. The amount of transcription is then compared to the amount of transcription in either the same cell in the absence of the test. compound or it may be compared with the amount of transcription in a substantially identical cell that lacks the specific receptors. A substantially identical cell may be derived from the same cells from which the recombinant cell was prepared but which had not been modified by introduction of heterologous DNA. Alternatively, it may be a cell in which the specific receptors are removed. Any statistically or otherwise significant difference in the amount of transcription indicates that the test compound has in some manner altered the activity of the specific receptor.
If the test compound does not appear to enhance, activate or induce the activity of the cell surface protein, the assay may be repeated and modified by the introduction of a step in which the recombinant cell is first tested for the ability of a known agonist or activator of the specific receptor to activate transcription if the transcription is induced, the test compound is then assayed for its ability to inhibit, block or otherwise affect the activity of the agonist.
The transcription based assay is useful for identifying compounds that interact with any cell surface protein whose activity ultimately alters gene expression. In particular, the assays can be used to test functional ligand-receptor or ligand-ion channel interactions for a number of categories of cell surface-localized receptors, including: ligand-gated ion channels and voltage-gated ion channels, and G protein-coupled receptors.
Any transfectable cell that can express the desired cell surface protein in a manner such the protein functions to intracellularly transduce an extracellular signal may be used. The cells may be selected such that they endogenously express the cell surface protein or may be genetically engineered to do so. Many such cells are known to those of skill in the art. Such cells include, but are not limited to Ltk less than xe2x88x92 greater than  cells, PC12 cells and COS-7 cells.
The preparation of cells which express a receptor or ion channel and a reporter gene expression construct, and which are useful for testing compounds to assess their activities, is exemplified in the Examples provided herewith by reference to mammalian Ltk less than xe2x88x92 greater than  and COS-7 cell lines, which express the Type I human muscarinic (HM1) receptor and which are transformed with either a c-fos promoter-CAT reporter gene expression construct or a c-fos promoter-luciferase reporter gene expression construct.
Any cell surface protein that is known to those of skill in the art or that may be identified by those of skill in the art may used in the assay. The cell surface protein may endogenously expressed on the selected cell or it may be expressed from cloned DNA. Exemplary cell surface proteins include, but are not limited to, cell surface receptors and ion channels. Cell surface receptors include, but are not limited to, muscarinic receptors (e.g.,, human M2 (GenBank accession #M16404); rat M3 (GenBank accession #M16407); human M4 (GenBank accession #M16405); human M5 (Bonner et al. (1988) Neuron 1:403-410); and the like); neuronal nicotinic acetylcholine receptors (e.g., the alpha 2, alpha 3 and beta 2 subtypes disclosed in U.S. Ser. No. 504,455 (filed Apr. 3, 1990), hereby expressly incorporated by reference herein in its entirety); the rat alpha 2 subunit (Wada et al. (1988) Science 240:330-334); the rat alpha 3 subunit (Boulter et al. (1986) Nature 319:368-374); the rat alpha 4 subunit (Goldman et al. (1987) cell 48:965-973); the rat alpha 5 subunit (Boulter et al. (1990) J. Biol. Chem. 265:4472-4482); the rat beta 2 subunit (Deneris et al. (1988) Neuron 1:45-54); the rat beta 3 subunit (Deneris et al. (1989) J. Biol. Chem. 264: 6268-6272); the rat beta 4 subunit (Duvoisin et al. (1989) Neuron 3:487-496); combinations of the rat alpha subunits, beta subunits and alpha and beta subunits; GABA receptors (e.g., the bovine alpha 1 and beta 1 subunits (Schofield et al. (1987) Nature 328:221-227); the bovine alpha 2 and alpha 3 subunits (Levitan et al. (1988) Nature 335:76-79); the gamma-subunit (Pritchett et al. (1989) Nature 338:582-585); the beta 2 and beta 3 subunits (Ymer et alo (1989) EMBO J. 8:1665-1670); the delta subunit (Shivers, B. D. (1989) Neuron 3:327-337); and the like); glutamate receptors (e.g., receptor isolated from rat brain (Hollmann et al. (1989) Nature 342:643-648); and the like); adrenergic receptors (e.g., human beta 1 (Frielle et al. (1987) Proc. Natl. Acad. Sci. 84.:7920-7924); human alpha 2 (Kobilka et al. (1987) Science 238:650-656); hamster beta 2 (Dixon et al. (1986) Nature 321:75-79); and the like); dopamine receptors (e.g., human D2 (Stormann et al. (1990) Molec. Pharm.37:1-6); rat (Bunzow et al. (1988) Nature 336:783-787); and the like); NGF receptors (e.g., human NGF receptors (Johnson et al. (1986) Cell 47:545-554); and the like); serotonin receptors (e.g., human 5HT1a (Kobilka et al. (1987) Nature 329:75-79); rat 5HT2 (Julius et al. (1990) PNAS 87:928-932); rat 5HT1c (Julius et al. (1988) Science 241:558-564); and the like).
Reporter gene constructs are prepared by operatively linking a reporter gene with at least one transcriptional regulatory element. If only one transcriptional regulatory element is included it must be a regulatable promoter, At least one of the selected transcriptional regulatory elements must be indirectly or directly regulated by the activity of the selected cell-surface receptor whereby activity of the receptor can be monitored via transcription of the reporter genes.
The construct may contain additional transcriptional regulatory elements, such as a FIRE sequence, or other sequence, that is not necessarily regulated by the cell surface protein, but is selected for its ability to reduce background level transcription or to amplify the transduced signal and to thereby increase the sensitivity and reliability of the assay.
Many reporter genes and transcriptional regulatory elements are known to those of skill in the art and others may be identified or synthesized by methods known to those of skill in the art.
A reporter gene includes any gene that expresses a detectable gene product, which may be RNA or protein. Preferred reporter genes are those that are readily detectable. The reporter gene may also be included in the construct in the form of a fusion gene with a gene that includes desired transcriptional regulatory sequences or exhibits other desirable properties.
Examples of reporter genes include, but are not limited to CAT (chloramphenicol acetyl transferase) (Alton and Vapnek (1979), Nature 282: 864-869) luciferase, and other enzyme detection systems, such as beta-galactosidase; firefly luciferase (deWet et al. (1987), Mol. Cell. Biol. 7:725-737); bacterial luciferase (Engebrecht and Silverman (1984), PNAS 1: 4154-4158; Baldwin et al. (1984), Biochemistry 23: 3663-3667); alkaline phosphatase (Toh et al. (1989) Eur. J. Biochem. 182: 231-238, Hall et al. (1983) J. Mol. Appl. Gen. 2: 101).
Transcriptional control elements include, but are not limited to, promoters, enhancers, and repressor and activator binding sites, Suitable transcriptional regulatory elements may be derived from the transcriptional regulatory regions of genes whose expression is rapidly induced, generally within minutes, of contact between the cell surface protein and the effector protein that modulates the activity of the cell surface protein. Examples of such genes include, but are not limited to, the immediate early genes (see, Sheng et al. (1990) Neuron 4: 477-485), such as c-fos, Immediate early genes are genes that are rapidly induced upon binding of a ligand to a cell surface protein. The transcriptional control elements that are preferred for use in the gene constructs include transcriptional control elements from immediate early genes, elements derived from other genes that exhibit some or all of the characteristics of the immediate early genes, or synthetic elements that are constructed such that genes in operative linkage therewith exhibit such characteristics. The characteristics of preferred genes from which the transcriptional control elements are derived include, but are not limited to, low or undetectable expression in quiescent cells, rapid induction at the transcriptional level within minutes of extracellular simulation, induction that is transient and independent of new protein synthesis, subsequent shut-off of transcription requires new protein synthesis, and mRNAs transcribed from these genes have a short half-life. It is not necessary for all of these properties to be present.
Pharmaceutical Compositions
In another aspect, the present invention provides pharmaceutically acceptable compositions which comprise a therapeutically-effective amount of one or more of the compounds described above, formulated together with one or more pharmaceutically acceptable carriers (additives) and/or diluents. As described in detail below, the pharmaceutical compositions of the present invention may be specially formulated for administration in solid or liquid form, including those adapted for the following: (1) oral administration, for example, drenches (aqueous or non-aqueous solutions or suspensions), tablets, boluses, powders, granules, pastes for application to the tongue; (2) parenteral administration, for example, by subcutaneous, intramuscular or intravenous injection as, for example, a sterile solution or suspension; (3) topical application, for example, as a cream, ointment or spray applied to the skin; or (4) intravaginally or intrarectally, for example, as a pessary, cream or foam.
The phrase xe2x80x9ctherapeutically-effective amountxe2x80x9d as used herein means that amount of a compound, material, or composition comprising a compound of the present invention which is effective for producing some desired therapeutic effect in at least a sub-population of cells in an animal at a reasonable benefit/risk ratio applicable to any medical treatment.
The phrase xe2x80x9cpharmaceutically acceptablexe2x80x9d is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio.
The phrase xe2x80x9cpharmaceutically-acceptable carrierxe2x80x9d as used herein means a pharmaceutically-acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, excipient, solvent or encapsulating material, involved in carrying or transporting the subject compound from one organ, or portion of the body, to another organ, or portion of the body. Each carrier must be xe2x80x9cacceptablexe2x80x9d in the sense of being compatible with the other ingredients of the formulation and not injurious to the patient. Some examples of materials which can serve as pharmaceutically-acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer""s solution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxic compatible substances employed in pharmaceutical formulations.
As set out above, certain embodiments of the present compounds may contain a basic functional group, such as amino or alkylamino, and are, thus, capable of forming pharmaceutically-acceptable salts with pharmaceutically-acceptable acids. The term xe2x80x9cpharmaceutically-acceptable saltsxe2x80x9d, refers to the relatively non-toxic, inorganic and organic acid addition salts of compounds of the present invention. These salts can be prepared in situ during the final isolation and purification of the compounds of the invention, or by separately reacting a purified compound of the invention in its free base form with a suitable organic or inorganic acid, and isolating the salt thus formed. Representative salts include the hydrobromide, hydrochloride, sulfate, bisulfate, phosphate, nitrate, acetate, valerate, oleate, palmitate, stearate, laurate, benzoate, lactate, phosphate, tosylate, citrate, maleate, fumarate, succinate, tartrate, napthylate, mesylate, glucoheptonate, lactobionate, and laurylsulphonate salts and the like. (See, for example, Berge et al. (1977) xe2x80x9cPharmaceutical Saltsxe2x80x9d, J. Pharm. Sci. 66:1-19)
The pharmaceutically acceptable salts of the subject compounds include the conventional nontoxic salts or quaternary ammonium salts of the compounds, e.g., from non-toxic organic or inorganic acids. For example, such conventional nontoxic salts include those derived from inorganic acids such as hydrochloride, hydrobromic, sulfuric, sulfamic, phosphoric, nitric, and the like; and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, palmitic, maleic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicyclic, sulfanilic, 2-acetoxybenzoic, fumaric, toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, isothionic, and the like.
In other cases, the compounds of the present invention may contain one or more acidic functional groups and, thus, are capable of forming pharmaceutically-acceptable salts with pharmaceutically-acceptable bases. The term xe2x80x9cpharmaceutically-acceptable saltsxe2x80x9d in these instances refers to the relatively non-toxic, inorganic and organic base addition salts of compounds of the present invention. These salts can likewise be prepared in situ during the final isolation and purification of the compounds, or by separately reacting the purified compound in its free acid form with a suitable base, such as the hydroxide, carbonate or bicarbonate of a pharmaceutically-acceptable metal cation, with ammonia, or with a pharmaceutically-acceptable organic primary, secondary or tertiary amine. Representative alkali or alkaline earth salts include the lithium, sodium, potassium, calcium, magnesium, and aluminum salts and the like. Representative organic amines useful for the formation of base addition salts include ethylamine, diethylamine, ethylenedianine, ethanolamine, diethanolarnine, piperazine and the like. (See, for example, Berge et al., supra)
Wetting agents, emulsifiers and lubricants, such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, release agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the compositions.
Examples of pharmaceutically-acceptable antioxidants include: (1) water soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate, alpha-tocopherol, and the like; and (3) metal chelating agents, such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol, tartaric acid, phosphoric acid, and the like.
Formulations of the present invention include those suitable for oral, nasal, topical (including buccal and sublingual), rectal, vaginal and/or parenteral administration. The formulations may conveniently be presented in unit dosage form and may be prepared by any methods well known in the art of pharmacy. The amount of active ingredient which can be combined with a carrier material to produce a single dosage form will vary depending upon the host being treated, the particular mode of administration. The amount of active ingredient which can be combined with a carrier material to produce a single dosage form will generally be that amount of the compound which produces a therapeutic effect. Generally, out of one hundred per cent, this amount will range from about 1 per cent to about ninety-nine percent of active ingredient, preferably from about 5 per cent to about 70 per cent, most preferably from about 10 per cent to about 30 per cent.
Methods of preparing these formulations or compositions include the step of bringing into association a compound of the present invention with the carrier and, optionally, one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association a compound of the present invention with liquid carriers, or finely divided solid carriers, or both, and then, if necessary, shaping the product.
Formulations of the invention suitable for oral administration may be in the form of capsules, cachets, pills, tablets, lozenges (using a flavored basis, usually sucrose and acacia or tragacanth), powders, granules, or as a solution or a suspension in an aqueous or non-aqueous liquid, or as an oil-in-water or water-in-oil liquid emulsion, or as an elixir or syrup, or as pastilles (using an inert base, such as gelatin and glycerin, or sucrose and acacia) and/or as mouth washes and the like, each containing a predetermined amount of a compound of the present invention as an active ingredient. A compound of the present invention may also be administered as a bolus, electuary or paste.
In solid dosage forms of the invention for oral administration (capsules, tablets, pills, dragees, powders, granules and the like), the active ingredient is mixed with one or more pharmaceutically-acceptable carriers, such as sodium citrate or dicalcium phosphate, and/or any of the following: (1) fillers or extenders, such as starches, lactose, sucrose, glucose, mannitol, and/or silicic acid; (2) binders, such as, for example, carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone, sucrose and/or acacia; (3) humectants, such as glycerol; (4) disintegrating agents, such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and sodium carbonate; (5) solution retarding agents, such as paraffin; (6) absorption accelerators, such as quaternary ammonium compounds; (7) wetting agents, such as, for example, cetyl alcohol and glycerol monostearate; (8) absorbents, such as kaolin and bentonite clay; (9) lubricants, such a talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, and mixtures thereof; and (10) coloring agents. In the case of capsules, tablets and pills, the pharmaceutical compositions may also comprise buffering agents. Solid compositions of a similar type may also be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugars, as well as high molecular weight polyethylene glycols and the like.
A tablet may be made by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared using binder (for example, gelatin or hydroxypropylmethyl cellulose), lubricant, inert diluent, preservative, disintegrant (for example, sodium starch glycolate or cross-linked sodium carboxymethyl cellulose), surface-active or dispersing agent. Molded tablets may be made by molding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent.
The tablets, and other solid dosage forms of the pharmaceutical compositions of the present invention, such as dragees, capsules, pills and granules, may optionally be scored or prepared with coatings and shells, such as enteric coatings and other coatings well known in the pharmaceutical-formulating art. They may also be formulated so as to provide slow or controlled release of the active ingredient therein using, for example, hydroxypropylmethyl cellulose in varying proportions to provide the desired release profile, other polymer matrices, liposomes and/or microspheres. They may be sterilized by, for example, filtration through a bacteria-retaining filter, or by incorporating sterilizing agents in the form of sterile solid compositions which can be dissolved in sterile water, or some other sterile injectable medium immediately before use. These compositions may also optionally contain opacifying agents and may be of a composition that they release the active ingredient(s) only, or preferentially, in a certain portion of the gastrointestinal tract, optionally, in a delayed manner. Examples of embedding compositions which can be used include polymeric substances and waxes. The active ingredient can also be in micro-encapsulated form, if appropriate, with one or more of the above-described excipients.
Liquid dosage forms for oral administration of the compounds of the invention include pharmaceutically acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. In addition to the active ingredient, the liquid dosage forms may contain inert diluents commonly used in the art, such as, for example, water or other solvents, solubilizing agents and emulsifiers, such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (in particular, cottonseed, groundnut, corn, germ, olive, castor and sesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan, and mixtures thereof.
Besides inert diluents, the oral compositions can also include adjuvants such as wetting agents, emulsifying and suspending agents, sweetening, flavoring, coloring, perfuming and preservative agents.
Suspensions, in addition to the active compounds, may contain suspending agents as, for example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth, and mixtures thereof.
Formulations of the pharmaceutical compositions of the invention for rectal or vaginal administration may be presented as a suppository, which may be prepared by mixing one or more compounds of the invention with one or more suitable nonirritating excipients or carriers comprising, for example, cocoa butter, polyethylene glycol, a suppository wax or a salicylate, and which is solid at room temperature, but liquid at body temperature and, therefore, will melt in the rectum or vaginal cavity and release the active compound.
Formulations of the present invention which are suitable for vaginal administration also include pessaries, tampons, creams, gels, pastes, foams or spray formulations containing such carriers as are known in the art to be appropriate.
Dosage forms for the topical or transdermal administration of a compound of this invention include powders, sprays, ointments, pastes, creams, lotions, gels, solutions, patches and inhalants. The active compound may be mixed under sterile conditions with a pharmaceutically-acceptable carrier, and with any preservatives, buffers, or propellants which may be required.
The ointments, pastes, creams and gels may contain, in addition to an active compound of this invention, excipients, such as animal and vegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonites, silicic acid, talc and zinc oxide, or mixtures thereof.
Powders and sprays can contain, in addition to a compound of this invention, excipients such as lactose, talc, silicic acid, aluminum hydroxide, calcium silicates and polyamide powder, or mixtures of these substances. Sprays can additionally contain customary propellants, such as chlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, such as butane and propane.
Transdermal patches have the added advantage of providing controlled delivery of a compound of the present invention to the body. Such dosage forms can be made by dissolving or dispersing the compound in the proper medium. Absorption enhancers can also be used to increase the flux of the compound across the skin. The rate of such flux can be controlled by either providing a rate controlling membrane or dispersing the compound in a polymer matrix or gel.
Ophthalmic formulations, eye ointments, powders, solutions and the like, are also contemplated as being within the scope of this invention.
Pharmaceutical compositions of this invention suitable for parenteral administration comprise one or more compounds of the invention in combination with one or more pharmaceutically-acceptable sterile isotonic aqueous or nonaqueous solutions, dispersions, suspensions or emulsions, or sterile powders which may be reconstituted into sterile injectable solutions or dispersions just prior to use, which may contain antioxidants, buffers, bacteriostats, solutes which render the formulation isotonic with the blood of the intended recipient or suspending or thickening agents.
Examples of suitable aqueous and nonaqueous carriers which may be employed in the pharmaceutical compositions of the invention include water, ethanol, polyols (such as glycerol, propylene glycol, polyethylene glycol, and the like), and suitable mixtures thereof, vegetable oils, such as olive oil, and injectable organic esters, such as ethyl oleate. Proper fluidity can be maintained, for example, by the use of coating materials, such as lecithin, by the maintenance of the required particle size in the case of dispersions, and by the use of surfactants.
These compositions may also contain adjuvants such as preservatives, wetting agents, emulsifying agents and dispersing agents. Prevention of the action of microorganisms upon the subject compounds may be ensured by the inclusion of various antibacterial and antifungal agents, for example, paraben, chlorobutanol, phenol sorbic acid, and the like. It may also be desirable to include isotonic agents, such as sugars, sodium chloride, and the like into the compositions. In addition, prolonged absorption of the injectable pharmaceutical form may be brought about by the inclusion of agents which delay absorption such as aluminum monostearate and gelatin.
In some cases, in order to prolong the effect of a drug, it is desirable to slow the absorption of the drug from subcutaneous or intramuscular injection. This may be accomplished by the use of a liquid suspension of crystalline or amorphous material having poor water solubility. The rate of absorption of the drug then depends upon its rate of dissolution which, in turn, may depend upon crystal size and crystalline form. Alternatively, delayed absorption of a parenterally-administered drug form is accomplished by dissolving or suspending the drug in an oil vehicle.
Injectable depot forms are made by forming microencapsule matrices of the subject compounds in biodegradable polymers such as polylactide-polyglycolide. Depending on the ratio of drug to polymer, and the nature of the particular polymer employed, the rate of drug release can be controlled. Examples of other biodegradable polymers include poly(orthoesters) and poly(anhydrides). Depot injectable formulations are also prepared by entrapping the drug in liposomes or microemulsions which are compatible with body tissue.
When the compounds of the present invention are administered as pharmaceuticals, to humans and animals, they can be given per se or as a pharmaceutical composition containing, for example, 0.1 to 99.5% (more preferably, 0.5 to 90%) of active ingredient in combination with a pharmaceutically acceptable carrier.
The preparations of the present invention may be given orally, parenterally, topically, or rectally. They are of course given in forms suitable for each administration route. For example, they are administered in tablets or capsule form, by injection, inhalation, eye lotion, ointment, suppository, etc. administration by injection, infusion or inhalation; topical by lotion or ointment; and rectal by suppositories. Oral administrations are preferred.
The phrases xe2x80x9cparenteral administrationxe2x80x9d and xe2x80x9cadministered parenterallyxe2x80x9d as used herein means modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticulare, subcapsular, subarachnoid, intraspinal and intrasternal injection and infusion.
The phrases xe2x80x9csystemic administration,xe2x80x9d xe2x80x9cadministered systemically,xe2x80x9d xe2x80x9cperipheral administrationxe2x80x9d and xe2x80x9cadministered peripherallyxe2x80x9d as used herein mean the administration of a compound, drug or other material other than directly into the central nervous system, such that it enters the patient""s system and, thus, is subject to metabolism and other like processes, for example, subcutaneous administration.
These compounds may be administered to humans and other animals for therapy by any suitable route of administration, including orally, nasally, as by, for example, a spray, rectally, intravaginally, parenterally, intracisternally and topically, as by powders, ointments or drops, including buccally and sublingually.
Regardless of the route of administration selected, the compounds of the present invention, which may be used in a suitable hydrated form, and/or the pharmaceutical compositions of the present invention, are formulated into pharmaceutically-acceptable dosage forms by conventional methods known to those of skill in the art.
Actual dosage levels of the active ingredients in the pharmaceutical compositions of this invention may be varied so as to obtain an amount of the active ingredient which is effective to achieve the desired therapeutic response for a particular patient, composition, and mode of administration, without being toxic to the patient.
The selected dosage level will depend upon a variety of factors including the activity of the particular compound of the present invention employed, or the ester, salt or amide thereof, the route of administration, the time of administration, the rate of excretion of the particular compound being employed, the duration of the treatment, other drugs, compounds and/or materials used in combination with the particular compound employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts.
A physician or veterinarian having ordinary skill in the art can readily determine and prescribe the effective amount of the pharmaceutical composition required. For example, the physician or veterinarian could start doses of the compounds of the invention employed in the pharmaceutical composition at levels lower than that required in order to achieve the desired therapeutic effect and gradually increase the dosage until the desired effect is achieved.
In general, a suitable daily dose of a compound of the invention will be that amount of the compound which is the lowest dose effective to produce a therapeutic effect. Such an effective dose will generally depend upon the factors described above. Generally, intravenous, intracerebroventricular and subcutaneous doses of the compounds of this invention for a patient, when used for the indicated analgesic effects, will range from about 0.0001 to about 100 mg per kilogram of body weight per day.
If desired, the effective daily dose of the active compound may be administered as two, three, four, five, six or more sub-doses administered separately at appropriate intervals throughout the day, optionally, in unit dosage forms.
While it is possible for a compound of the present invention to be administered alone, it is preferable to administer the compound as a pharmaceutical formulation (composition).
In another aspect, the present invention provides pharmaceutically acceptable compositions which comprise a therapeutically-effective amount of one or more of the subject co,pounds, as described above, formulated together with one or more pharmaceutically acceptable carriers (additives) and/or diluents. As described in detail below, the pharmaceutical compositions of the present invention may be specially formulated for administration in solid or liquid form, including those adapted for the following: (1) oral administration, for example, drenches (aqueous or non-aqueous solutions or suspensions), tablets, boluses, powders, granules, pastes for application to the tongue; (2) parenteral administration, for example, by subcutaneous, intramuscular or intravenous injection as, for example, a sterile solution or suspension; (3) topical application, for example, as a cream, ointment or spray applied to the skin; or (4) intravaginally or intravectally, for example, as a pessary, cream or foam.
The compounds according to the invention may be formulated for administration in any convenient way for use in human or veterinary medicine, by analogy with other pharmaceuticals.
The term xe2x80x9ctreatmentxe2x80x9d is intended to encompass also prophylaxis, therapy and cure.
The patient receiving this treatment is any animal in need, including primates, in particular humans, and other mammals such as equines, cattle, swine and sheep; and poultry and pets in general.
The compound of the invention can be administered as such or in admixtures with pharmaceutically acceptable carriers and can also be administered in conjunction with antimicrobial agents such as penicillins, cephalosporins, aminoglycosides and glycopeptides. Conjunctive therapy, thus includes sequential, simultaneous and separate administration of the active compound in a way that the therapeutical effects of the first administered one is not entirely disappeared when the subsequent is administered.
The addition of the active compound of the invention to animal feed is preferably accomplished by preparing an appropriate feed premix containing the active compound in an effective amount and incorporating the premix into the complete ration.
Alternatively, an intermediate concentrate or feed supplement containing the active ingredient can be blended into the feed. The way in which such feed premixes and complete rations can be prepared and administered are described in reference books (such as xe2x80x9cApplied Animal Nutritionxe2x80x9d, W. H. Freedman and CO., San Francisco, U.S.A., 1969 or xe2x80x9cLivestock Feeds and Feedingxe2x80x9d O and B books, Corvallis, Ore., U.S.A., 1977).
Combinatorial Libraries
The subject reactions readily lend themselves to the creation of combinatorial libraries of compounds for the screening of pharmaceutical, agrochemical or other biological or medically-related activity or material-related qualities. A combinatorial library for the purposes of the present invention is a mixture of chemically related compounds which may be screened together for a desired property; said libraries may be in solution or covalently linked to a solid support. The preparation of many related compounds in a single reaction greatly reduces and simplifies the number of screening processes which need to be carried out. Screening for the appropriate biological, pharmaceutical, agrochemical or physical property may be done by conventional methods.
Diversity in a library can be created at a variety of different levels. For instance, the substrate aryl groups used in a combinatorial approach can be diverse in terms of the core aryl moiety, e.g., a variegation in terms of the ring structure, and/or can be varied with respect to the other substituents.
A variety of techniques are available in the art for generating combinatorial libraries of small organic molecules. See, for example, Blondelle et al. (1995) Trends Anal. Chem. 14:83; the Affymax U.S. Pat. Nos. 5,359,115 and 5,362,899: the Ellman U.S. Pat. No. 5,288,514: the Still et al. PCT publication WO 94/08051; Chen et al. (1994) JACS 116:2661: Kerr et al. (1993) JACS 115:252; PCT publications WO92/10092, WO93/09668 and WO91/07087; and the Lerner et al. PCT publication WO93/20242). Accordingly, a variety of libraries on the order of about 16 to 1,000,000 or more diversomers can be synthesized and screened for a particular activity or property.
In an exemplary embodiment, a library of substituted diversomers can be synthesized using the subject reactions adapted to the techniques described in the Still et al. PCT publication WO 94/08051, e.g., being linked to a polymer bead by a hydrolyzable or photolyzable group, e.g., located at one of the positions of substrate. According to the Still et al. technique, the library is synthesized on a set of beads, each bead including a set of tags identifying the particular diversomer on that bead. In one embodiment, which is particularly suitable for discovering enzyme inhibitors, the beads can be dispersed on the surface of a permeable membrane, and the diversomers released from the beads by lysis of the bead linker. The diversomer from each bead will diffuse across the membrane to an assay zone, where it will interact with an enzyme assay. Detailed descriptions of a number of combinatorial methodologies are provided below.
A. Direct Characterization
A growing trend in the field of combinatorial chemistry is to exploit the sensitivity of techniques such as mass spectrometry (MS), e.g., which can be used to characterize sub-femtomolar amounts of a compound, and to directly determine the chemical constitution of a compound selected from a combinatorial library. For instance, where the library is provided on an insoluble support matrix, discrete populations of compounds can be first released from the support and characterized by MS. In other embodiments, as part of the MS sample preparation technique, such MS techniques as MALDI can be used to release a compound from the matrix, particularly where a labile bond is used originally to tether the compound to the matrix. For instance, a bead selected from a library can be irradiated in a MALDI step in order to release the diversomer from the matrix, and ionize the diversomer for MS analysis.
B) Multipin Synthesis
The libraries of the subject method can take the multipin library format. Briefly, Geysen and co-workers (Geysen et al. (1984) PNAS 81:3998-4002) introduced a method for generating compound libraries by a parallel synthesis on polyacrylic acid-grated polyethylene pins arrayed in the microtitre plate format. The Geysen technique can be used to synthesize and screen thousands of compounds per week using the multipin method, and the tethered compounds may be reused in many assays. Appropriate linker moieties can also been appended to the pins so that the compounds may be cleaved from the supports after synthesis for assessment of purity and further evaluation (c.f., Bray et al. (1990) Tetrahedron Lett 31:5811-5814; Valerio et al. (1991) Anal Biochem 197:168-177; Bray et al. (1991) Tetrahedron Lett 32:6163-6166).
C) Divide-Couple-Recombine
In yet another embodiment, a variegated library of compounds can be provided on a set of beads utilizing the strategy of divide-couple-recombine (see, e.g., Houghten (1985) PNAS 82:5131-5135; and U.S. Pat. Nos. 4,631,211; 5,440,016; 5,480,971). Briefly, as the name implies, at each synthesis step where degeneracy is introduced into the library, the beads are divided into separate groups equal to the number of different substituents to be added at a particular position in the library, the different substituents coupled in separate reactions, and the beads recombined into one pool for the next iteration.
In one embodiment, the divide-couple-recombine strategy can be carried out using an analogous approach to the so-called xe2x80x9ctea bagxe2x80x9d method first developed by Houghten, where compound synthesis occurs on resin sealed inside porous polypropylene bags (Houghten et al. (1986) PNAS 82:5131-5135). Substituents are coupled to the compound-bearing resins by placing the bags in appropriate reaction solutions, while all common steps such as resin washing and deprotection are performed simultaneously in one reaction vessel. At the end of the synthesis, each bag contains a single compound.
D) Combinatorial Libraries by Light-Directed, Spatially Addressable Parallel Chemical Synthesis
A scheme of combinatorial synthesis in which the identity of a compound is given by its locations on a synthesis substrate is termed a spatially-addressable synthesis. In one embodiment, the combinatorial process is carried out by controlling the addition of a chemical reagent to specific locations on a solid support (Dower et al. (1991) Annu Rep Med Chem 26:271-280; Fodor, S.P.A. (1991) Science 251:767; Pirrung et al. (1992) U.S. Pat. No. 5,143,854; Jacobs et al. (1994) Trends Biotechnol 12:19-26). The spatial resolution of photolithography affords miniaturization. This technique can be carried out through the use protection/deprotection reactions with photolabile protecting groups.
The key points of this technology are illustrated in Gallop et al. (1994) J Med Chem 37:1233-1251. A synthesis substrate is prepared for coupling through the covalent attachment of photolabile nitroveratryloxycarbonyl (NVOC) protected amino linkers or other photolabile linkers. Light is used to selectively activate a specified region of the synthesis support for coupling. Removal of the photolabile protecting groups by light (deprotection) results in activation of selected areas. After activation, the first of a set of amino acid analogs, each bearing a photolabile protecting group on the amino terminus, is exposed to the entire surface. Coupling only occurs in regions that were addressed by light in the preceding step. The reaction is stopped, the plates washed, and the substrate is again illuminated through a second mask, activating a different region for reaction with a second protected building block. The pattern of masks and the sequence of reactants define the products and their locations. Since this process utilizes photolithography techniques, the number of compounds that can be synthesized is limited only by the number of synthesis sites that can be addressed with appropriate resolution. The position of each compound is precisely known; hence, its interactions with other molecules can be directly assessed.
In a light-directed chemical synthesis, the products depend on the pattern of illumination and on the order of addition of reactants. By varying the lithographic patterns, many different sets of test compounds can be synthesized simultaneously; this characteristic leads to the generation of many different masking strategies.
E) Encoded Combinatorial Libraries
In yet another embodiment, the subject method utilizes a compound library provided with an encoded tagging system. A recent improvement in the identification of active compounds from combinatorial libraries employs chemical indexing systems using tags that uniquely encode the reaction steps a given bead has undergone and, by inference, the structure it carries. Conceptually, this approach mimics phage display libraries, where activity derives from expressed peptides, but the structures of the active peptides are deduced from the corresponding genomic DNA sequence. The first encoding of synthetic combinatorial libraries employed DNA as the code. A variety of other forms of encoding have been reported, including encoding with sequenceable bio-oligomers (e.g., oligonucleotides and peptides), and binary encoding with additional non-sequenceable tags.
1) Tagging with Sequenceable Bio-oligomers
The principle of using oligonucleotides to encode combinatorial synthetic libraries was described in 1992 (Brenner et al. (1992) PNAS 89:5381-5383), and an example of such a library appeared the following year (Needles et al. (1993) PNAS 90:10700-10704). A combinatorial library of nominally 77 (=823,543) peptides composed of all combinations of Arg, Gln, Phe, Lys, Val, D-Val and Thr (three-letter amino acid code), each of which was encoded by a specific dinucleotide (TA, TC, CT, AT, TT, CA and AC, respectively), was prepared by a series of alternating rounds of peptide and oligonucleotide synthesis on solid support. In this work, the amine linking functionality on the bead was specifically differentiated toward peptide or oligonucleotide synthesis by simultaneously preincubating the beads with reagents that generate protected OH groups for oligonucleotide synthesis and protected NH2 groups for peptide synthesis (here, in a ratio of 1:20). When complete, the tags each consisted of 69-mers, 14 units of which carried the code. The bead-bound library was incubated with a fluorescently labeled antibody, and beads containing bound antibody that fluoresced strongly were harvested by fluorescence-activated cell sorting (FACS). The DNA tags were amplified by PCR and sequenced, and the predicted peptides were synthesized. Following such techniques, compound libraries can be derived for use in the subject method, where the oligonucleotide sequence of the tag identifies the sequential combinatorial reactions that a particular bead underwent, and therefore provides the identity of the compound on the bead.
The use of oligonucleotide tags permits exquisitely sensitive tag analysis. Even so, the method requires careful choice of orthogonal sets of protecting groups required for alternating co-synthesis of the tag and the library member. Furthermore, the chemical lability of the tag, particularly the phosphate and sugar anomeric linkages, may limit the choice of reagents and conditions that can be employed for the synthesis of non-oligomeric libraries. In preferred embodiments, the libraries employ linkers permitting selective detachment of the test compound library member for assay.
Peptides have also been employed as tagging molecules for combinatorial libraries. Two exemplary approaches are described in the art, both of which employ branched linkers to solid phase upon which coding and ligand strands are alternately elaborated. In the first approach (Kerr JM et al. (1993) J Am Chem Soc 115:2529-2531), orthogonality in synthesis is achieved by employing acid-labile protection for the coding strand and base-labile protection for the compound strand.
In an alternative approach (Nikolaiev et al. (1993) Pept Res 6:161-170), branched linkers are employed so that the coding unit and the test compound can both be attached to the same functional group on the resin. In one embodiment, a cleavable linker can be placed between the branch point and the bead so that cleavage releases a molecule containing both code and the compound (Ptek et al. (1991) Tetrahedron Lett 32:3891-3894). In another embodiment, the cleavable linker can be placed so that the test compound can be selectively separated from the bead, leaving the code behind. This last construct is particularly valuable because it permits screening of the test compound without potential interference of the coding groups. Examples in the art of independent cleavage and sequencing of peptide library members and their corresponding tags has confirmed that the tags can accurately predict the peptide structure.
2) Non-sequenceable Tagging: Binary Encoding
An alternative form of encoding the test compound library employs a set of non-sequencable electrophoric tagging molecules that are used as a binary code (Ohlmeyer et al. (1993) PNAS 90:10922-10926). Exemplary tags are haloaromatic alkyl ethers that are detectable as their trimethylsilyl ethers at less than femtomolar levels by electron capture gas chromatography (ECGC). Variations in the length of the alkyl chain, as well as the nature and position of the aromatic halide substituents, permit the synthesis of at least 40 such tags, which in principle can encode 240 (e.g., upwards of 1012) different molecules. In the original report (Ohlmeyer et al., supra) the tags were bound to about 1% of the available amine groups of a peptide library via a photocleavable o-nitrobenzyl linker. This approach is convenient when preparing combinatorial libraries of peptide-like or other amine-containing molecules. A more versatile system has, however, been developed that permits encoding of essentially any combinatorial library. Here, the compound would be attached to the solid support via the photocleavable linker and the tag is attached through a catechol ether linker via carbene insertion into the bead matrix (Nestler et al. (1994) J Org Chem 59:4723-4724). This orthogonal attachment strategy permits the selective detachment of library members for assay in solution and subsequent decoding by ECGC after oxidative detachment of the tag sets.
Although several amide-linked libraries in the art employ binary encoding with the electrophoric tags attached to amine groups, attaching these tags directly to the bead matrix provides far greater versatility in the structures that can be prepared in encoded combinatorial libraries. Attached in this way, the tags and their linker are nearly as unreactive as the bead matrix itself. Two binary-encoded combinatorial libraries have been reported where the electrophoric tags are attached directly to the solid phase (Ohlmeyer et al. (1995) PNAS 92:6027-6031) and provide guidance for generating the subject compound library. Both libraries were constructed using an orthogonal attachment strategy in which the library member was linked to the solid support by a photolabile linker and the tags were attached through a linker cleavable only by vigorous oxidation. Because the library members can be repetitively partially photoeluted from the solid support, library members can be utilized in multiple assays. Successive photoelution also permits a very high throughput iterative screening strategy: first, multiple beads are placed in 96-well microtiter plates; second, compounds are partially detached and transferred to assay plates; third, a metal binding assay identifies the active wells; fourth, the corresponding beads are rearrayed singly into new microtiter plates; fifth, single active compounds are identified; and sixth, the structures are decoded.